If you were to survey what analytic philosophers have said about God’s omniscience over the past 50 years or so, you’d find that the vast majority of them define omniscience in strictly propositional terms. For example, William Lane Craig in vol. 2a of his recent Systematic Philosophical Theology (2025), defends the following definition of omniscience (p. 203):
(Oprop) S is omniscient =def. For all propositions, p, if p, then S knows that p and does not believe that ~p
In normal English, Oprop (for “propositional omniscience”) says that an omniscient being knows all truths and believes no falsehoods. Some proposed analyses of omniscience are more elaborate than this, but in nearly all cases the objects of an omniscient being’s knowledge are said to be propositions. Regardless of how elaborate the proposed analysis may be, I believe a proposition-focused approach is a bad way to think about omniscience.
A better approach, one that gets much closer to the intuitive and Scriptural (see Heb. 4:13 and 1 Cor. 2:11) idea that God has perfect and exhaustive knowledge of all of reality is captured by Ofull (for “full omniscience”):
(Ofull) S is omniscient =def. S knows all of reality as well as it can possibly be known.
I argue for and unpack Ofull in what follows. I begin (§1) by stepping back from omniscience to the more basic concept of knowledge and present a brief history of efforts to define it. I then (§2) offer three reasons for thinking that a strictly propositional approach to knowledge is inadequate. I next (§3) discuss various strategies for defining concepts in general and argue that the only promising approach for defining knowledge begins with the realization that it as a degreed perfection concept. As such, we can’t define knowledge by specifying necessary and sufficient conditions. What we can do is identify clear examples of lower-grade knowledge and extrapolate from them toward the idea of perfect knowledge or full omniscience as the absolute limit case of knowledge. In §4 I begin to unpack what perfect knowledge looks like by distinguishing four tiers of knowledge ranging from the experiential lowest (animal knowledge) to the theoretical highest (divine knowledge). In §5 I explore the perfect or divine tier of knowledge by identifying nine dimensions along which knowledge can vary in perfection. When knowledge is maximized along all nine dimensions, we arrive at a good understanding of what divine knowledge / full omniscience entails.
1. What is knowledge? A brief history
Philosophers have typically sought to define the concept of knowledge (Greek, episteme) in terms of necessary and sufficient conditions (see §3 for an explanation of this). For most of over two thousand years the general consensus followed Plato in thinking of knowledge as “justified true belief.” With some variations as to what counts as epistemic justification, medieval thinkers following Aristotle often supposed that knowledge properly speaking (Latin, scientia) required decisive justification, whether by direct illumination or rational apprehension or by demonstration via a connected series of such apprehensions. Early modern thinkers, writing in the wake of the nominalist revolution, the Copernican revolution, and the Protestant Reformation, were on the whole rather skeptical about the possibility of decisive justification. Even if, as rationalists like Descartes, Spinoza, and Leibniz supposed, certain rational principles could be known with mathematical certainty, knowledge broadly speaking was increasingly regarded as fallible and probabilistic rather than requiring decisive justification.
Once knowledge became separated from decisive justification, the concept of knowledge as “justified true belief” became unstable, as there was no longer any way to ensure that the justification and truth conditions remain in sync. In 1963 a famous paper by Edmund Gettier exploited this and showed through counterexamples that it was possible to have justified true belief without having knowledge. This paper spurred epistemologists into a three decade-long struggle to either identify a fourth condition in addition to justification, truth, and belief for defining knowledge or to reconceive and/or replace justification with other concepts like reliability and warrant. But philosophers couldn’t agree on a new set of necessary and sufficient conditions for knowledge and eventually sidelined that controversy to focus on more tractable topics like the nature of evidence, Bayesian epistemology, social epistemology, and the like. Some of them even decried the whole project of defining knowledge and suggested taking it as an undefinable, basic concept.
I believe much of this philosophical trajectory was misguided in two main ways. First, as I argue in §2, knowledge isn’t exclusively or even fundamentally propositional and so its definition shouldn’t be centered on the truth or justification of beliefs, that is, of belief contents (i.e., propositions). Second, as I argue in §3, knowledge is a degreed perfection concept and so was never a suitable candidate for definition in terms of necessary and sufficient conditions.
2. Why propositional definitions of knowledge are inadequate
To be clear, I have no objection to the ideas that there is such a thing as propositional knowledge and that God, as omniscient, has all available knowledge of that sort. What I object to are the ideas that omniscience and knowledge generally should be defined as propositional, that is, as knowledge of propositions. I object to this for three reasons.
First, there is much more to knowledge than propositional knowledge. Propositional knowledge, which Bertrand Russell called “knowledge by description,” is abstract. That is, it lies at least one step removed from concrete reality. In this respect, propositional knowledge contrasts with what Russell called “knowledge by acquaintance.” There is, for example, a clear difference between knowing the proposition <Tat the cat is on the mat> and having first-hand acquaintance with Tat and the concrete situation of Tat’s being on the mat. The proposition can be known, assuming it’s true, simply by overhearing a second-hand report from a reliable source, but the concrete reality that proposition represents can only be known by being there first-hand. Knowing a concrete individual like a person is not reducible to knowing true propositions about that person.
Second, by its very nature propositional knowledge is analytic. It breaks meaning down into discrete statement-sized chunks. In so doing it makes meaning digital, and thereby overlooks the analog, the holistic, the synthetic. But deep and practical knowledge of any subject matter is holistic and synthetic. It requires understanding connections between things, and not just abstract logical connections among propositions (i.e., more propositions), but the concrete real-world connections they represent. For example, knowing how to ride a bike involves much more than internalizing a list of true bike-riding propositions. It requires a performative ability to handle a bike in concrete circumstances. Contemplating a list of propositions while trying to ride a bike would only get in the way and make one more likely to fall over or crash.
Third, knowledge requires both a knower and a known, a knowing subject and known object. Propositional knowledge puts the emphasis almost entirely on the known, thereby sidelining the knower. Indeed, the knower is often represented generically by philosophers with the letter “S” because we really aren’t interested in the knower. This skews our understanding of knowledge. Thus, a propositionally-focused approach naturally lends itself to quantitative or extensional questions such as whether S knows that p and what it is for S to know that p. These are fine questions in themselves, but in many contexts, such as when a knowledge claim is contested, it’s at least as important to address the qualitative or intensional question of how well someone knows, or is in a position to know, some claim. This requires that we keep both the knower and the known in focus. For example, first-hand testimony normally counts for more than second-hand testimony or “hearsay.” The first-hand closeness or proximity of the knower to the known is often qualitatively relevant. If two people know the same proposition, but one knows it first-hand and the other only knows it second-hand by way of testimony from the first person, then there is a clear sense in which the first knower’s knowledge is better than the second knower’s knowledge.
3. Knowledge as a degreed perfection concept
There are several different ways one might try to define a concept. First, a lexical definition is what you get from a dictionary. A dictionary describes word usage. But we want to define a concept (knowledge), not a word. The two are related, of course, as words are typically used to express concepts, but words are also notoriously polysemous. That is, they often have multiple, distinct usages and therefore can express multiple, distinct concepts. Consequently, while consulting a dictionary is often a decent starting place for thinking about a concept, it’s rarely a good place to stop. By itself it can’t tell us which, if any, of the listed usages are what we need. Second, a stipulative definition is what we offer when we stipulate that “by term ‘X’ I mean” followed by a description of how one intends to use term ‘X’. This circumvents the polysemy problem, but at the expense of arbitrariness. Why should anyone else accept our stipulations? Third, an ostensive definition avoids arbitrariness by pointing at a clear example. This is how most basic words are introduced. To teach a child what the word “duck” means, for example, you say the word while pointing at a duck or a clear picture of a duck. But not all concepts have clear examples that can be pointed at (e.g., God, infinity, nothing, etc.) and simply pointing at something doesn’t tell us explicitly what makes that thing a good example. Fourth, a conceptual definition helps us understand a concept by connecting it to other concepts, ones we (hopefully) already understand. In standard form a conceptual definition specifies a genus (what kind of thing we’re interested in) and a specific difference (how it differs from other things of the same kind). For example, we can define a circle as a two-dimensional closed shape (its genus) the entire boundary of which is equidistant from a fixed point (its specific difference). A good conceptual definition articulates necessary and sufficient conditions for the application of a concept. Not all concepts can be defined in this way, however. This is especially true when the concept is vague, i.e., has a “fuzzy” boundary. In such cases we may be able to specify an inner boundary (sufficient but not necessary) and an outer boundary (necessary but not sufficient), but there remains a “grey area” between those boundaries where it’s not clear whether the concept applies or not. Most degreed or “spectrum” concepts fall into this problem category. For example, where does red begin and end on the color spectrum? There’s no precise answer. (Yes, we can stipulate precise boundaries for red, but then we’re no longer offering a conceptual definition but a stipulative one.) The same issue applies to most perfection concepts, for example, goodness. Goodness isn’t all or nothing; it comes in degrees. We have an outer (or lower) boundary—some things (e.g., murder) are clearly not good. But we don’t have an inner (or upper) boundary because there’s no point at which goodness becomes literally too good so as to be not good. Nor can we even clearly conceive of what the absolute limit case of goodness looks like. So, we can’t give necessary and sufficient conditions in a way that removes all vagueness.
To define a degreed perfection concept like goodness our only option is to combine aspects of ostensive and conceptual definitions and then project it toward “perfection” insofar as we can grasp it. We first focus on the clearest, most paradigmatic examples of the concept we can find in our experience. That’s the ostensive component. But, however clear these examples, they may still be far from absolute perfection. This is the case when perfection lies beyond anything we can experience, such as with omniscience or perfect goodness. Next, we use our understanding of the cases we can experience to reflect on how those cases could theoretically be improved. This helps us identify some of the concept’s necessary conditions. That’s the conceptual component. Necessary conditions define the concept’s outer (or lower) boundary. These are baseline features that never vary or drop out as we consider how our paradigmatic examples might be improved. Third, the variant features, those respects in which even our best examples of the concept can be improved, define a “vector” that points us in the general direction of absolute perfection. The perfect degree of the concept is thus understood by analogy with the paradigmatic cases from which we started. They provide an experiential anchor that keeps the concept grounded even as it points us toward a perfection that lies beyond us.
This is how I propose to approach the concept of knowledge. But first I need to address some critical questions.
First, why should we think of knowledge as a degreed concept? Because it rather obviously is. All of the concepts chiefly used to define knowledge—justification, truth, reliability, belief, warrant, probability, credence, relevance, salience, grounds, evidence, etc.—as well as many closely related concepts—understanding, wisdom, know-how, etc.—all admit of degrees in one way or another. Thus, one can have more or less justification, warrant, grounds, or evidence for a claim. The evidence one has for a claim can be more or less relevant or salient to it. It can have a greater or lesser effect on the probability of the claim. The processes by which one forms a belief or acquires evidence can be more or less reliable. One can have a stronger or weaker belief in the claim, or place more or less credence in it. A claim can be more or less true, that is, it can correspond more or less closely with reality. As for related concepts, one can have more or less understanding of a matter, have more or less wisdom, more or less know-how, and, finally, more or less knowledge. In short, if all of the concepts surrounding knowledge admit of degrees, it’s really hard to see how knowledge could fail to admit of degrees. That knowledge is a degreed concept should not, therefore, be controversial. A priori it is much more plausible than its denial.
Second, why should we think of knowledge as a perfection concept? Because it’s obvious that goodness is a perfection concept and that having knowledge of what is good is categorically better than lacking knowledge of what is good. Sure, we sometimes say “ignorance is bliss” because we think there are things that are not good that we’d be better off not knowing about. And, I’ll concede that if reality were fundamentally bad or neutral, then knowledge could turn out to be more of curse than a perfection. But, as a Christian theist committed to the existence of a perfectly good and loving God as the singular foundation of reality, that knowledge is a perfection concept like goodness concept seems undeniable to me. For a perfect being like God, even bad things are worth knowing because (a) they can’t overwhelm Him, (b) nothing bad is all bad but is rather a corruption of something otherwise good, and (c) knowing bad things is a necessary first step toward turning them back toward the good.
Third, if knowledge is degreed perfection concept, why shouldn’t we just identify knowledge with perfect knowledge and say that everything short of that isn’t knowledge at all? Because this is a self-defeating skeptical proposal that, if adopted, would leave us no way to reason analogically from lower-level instances of knowledge (because there would be no such instances) and would thereby make it impossible for us to develop any clear idea of perfect knowledge. Furthermore, we have already established that knowledge is a degreed concept. We can’t affirm that and also equate knowledge with only the highest degree. That would be inconsistent. Finally, a noteworthy feature of degreed concepts is that their applicability is normally a matter of pragmatic judgment. We say, for example, that a desk or table is “flat” knowing full well that if we were to zoom in closely with a powerful microscope the surface would present as anything but flat at the micro level. We can, of course, conceive of a surface being strictly or perfectly flat, but if we were to restrict our usage of the word “flat” to refer only to things that are perfectly flat, then the term would become nearly useless. When we say that a surface, like this table or Nebraska, is “flat” we mean that it is flat enough for the practical purposes we currently care about. Likewise, we can say that a certain proposition (e.g., “pi = 3.14”) is “true” even when we know that it is strictly false provided it is true enough for our current practical context. One who protested and said “Oh, but that’s not really flat, not really true, etc.” to point out that in most contexts degreed concepts don’t strictly apply—something we already know—would be a pedantic and socially inept jerk. Likewise with knowledge. If knowledge is a degreed concept, then the question of whether S knows (by description) proposition p or knows (by acquaintance) entity e, becomes a matter for pragmatic judgment. Does S know p or e well enough in the relevant context? The exception, of course, is the ideal or perfect case. Like a mathematical plane stipulated to be perfectly flat, if there is a coherent conception of perfect knowledge, then any instance of that sort of knowledge would have to be knowledge strictly so-called, knowledge full stop. But this is no more reason to refuse attributing “knowledge” to less-than-perfect instances than a desk’s not being perfectly flat is a reason to deny that it is, in a relevantly approximate sense, flat.
4. Knowledge: animal, human, and divine
To the extent I can, I’m going to try to unpack the concept of perfect knowledge by considering clear-cut cases of animal- and human-level knowledge, noting what they reveal as necessary or invariant about knowledge and what they reveal as variable dimensions along which knowledge can theoretically be improved. The result will be an analogical conception of omniscience as perfect knowledge that gives us insight into the “as well as it can possibly be known” clause of Ofull.
Consider the following three levels or tiers of knowledge:
Tier 1: Animal knowledge. This kind of knowledge is unreflective and often instinctual. My dog Misa knows when I say to her “Where’s your toy?” that I’m talking about one of her squeaky toys, and she knows if she can’t find a toy in her immediate vicinity she can get one from the doggie toy box downstairs. Likewise, many animals know instinctively what sort of food they need; when it’s time to mate, migrate, hunt, or hibernate; how to build a proper nest; and how to navigate long distances back to their breeding grounds. As far as we can tell, animals don’t encode knowledge propositionally and don’t self-reflectively consider whether or how they know such things. But that they do know many things is demonstrated by their ability repeatedly to navigate the world successfully to obtain their goals.
Tier 2: Casual human knowledge. Most of our everyday knowledge is of this sort. We know who the President is; how to ride a bike; that we’ve got to do X, Y, and Z by next Thursday; how to state and apply the Pythagorean theorem; etc. This kind of knowledge is partly self-reflective and often at least partially propositionally articulated. It is acquired experientially and often linguistically through instruction, reading, and observation. It’s partly self-reflective because we sometimes wonder whether and how we know what we think we know, and we often consciously try to consider things from different perspectives.
Tier 3: Expert human knowledge. This kind of knowledge is highly self-reflective, highly articulate, and accompanied by deep understanding of some domain. The best way to understand this is by contrast with casual human knowledge. A causal math student, for example, can be said to know the Central Limit Theorem after having just read about it in an introductory statistics text, but the mathematician who wrote the text knows the theorem in a qualitatively deeper sense. He (we may plausibly assume) not only knows how to state the theorem with precision, but can rigorously prove it in half a dozen independent ways and apply it correctly and creatively across a diverse range of contexts. The casual math student can’t do any of that.
My first observation in reflecting on these tiers is that all of them qualify as knowledge. Knowledge at the animal and causal human level isn’t a difficult achievement. It’s rather commonplace. All it requires at a minimum are the abilities to recognize meaningful patterns in experience and to navigate the world successfully (for the most part) on that basis. It doesn’t require self-conscious reflection, deep understanding, or propositional articulation. Most of us, for example, know how to ride a bike, but how many of us can describe with any precision how to do so?
My second observation is that as we move up the tiers, more is required. We arrive at qualitatively better grades of knowledge. All other things equal, knowledge systems that are articulate, self-reflective, and rooted in deep understanding track reality more closely over time and can withstand more scrutiny. There is a clear trajectory of improvement as we move from animal knowledge to casual human knowledge to expert human knowledge.
My third observation is that expert human level knowledge is nowhere near the maximum. If we continue the same trajectory of improvement from tiers 1–3 we can at least begin to catch a glimpse of what perfect knowledge is like. Everything points toward a fourth tier of knowledge, divine knowledge, that preserves all of the core strengths of tiers 1–3 while surmounting their limitations. To make matters more precise, I will now argue that there are at least nine respects in which knowledge can be improved as we move from animal knowledge to divine knowledge.
5. Nine aspects of perfect, divine knowledge
From our own experience, let’s think about ways in which low-tier knowledge can be improved or enhanced. Just as the expert human knows things in his area of expertise better than a casual human knower does, so a divine knower like God knows things better than even the most competent human experts do.
I believe there are at least nine ways in which low-tier knowledge can be improved:
- Scope: One can become a better knower by knowing more. More knowledge is a precondition for greater understanding and wisdom. The scope of perfect, divine knowledge extends to all of reality.
- Accuracy: Improved accuracy means that one’s knowledge is truer, in closer sync with reality. Perfect, divine knowledge would have maximum accuracy. God would know reality exactly as it is.
- Retention: Animal and human knowledge can be lost. We are forgetful. Perfect, divine knowledge would be maintained by perfect memory. God cannot literally “forget.”
Side note: While Heb. 8:12 and Heb. 10:17 say that God will remember our sins no more, these do not mean that God will literally forget them. The context indicates that God will no longer make an issue of our past sins because they have been dealt with.
- Immediacy: Animal and human knowledge is mediated by the transmission of sensory information, which depends on photons, sound waves, nerve signals, etc. But just as more immediate, first-hand knowledge is (all other things equal) better than second-hand knowledge, perfect, divine knowledge would have no dependence on information transmission. God knows all of reality immediately. As Heb. 4:13 says, all of creation lies “naked and exposed” to God.
- Reflexive transparency: Sometimes we not only know, but we know that we know. We then have higher-order knowledge. But for us this is the exception, not the rule. For a perfect, divine knower it is the rule. This is a corollary of #1 (maximal scope). Whenever God knows proposition p or entity e, God knows that He knows those things and knows that He knows that He knows them, and so on, ad infinitum. The reason this infinite sequence isn’t problematic is because of #4 (immediacy). The immediacy of God’s knowledge allows God’s higher-order knowledge to be fully transparent or such that it doesn’t require any new or additional information. For God to know that He knows p is just for God to know p, nothing more.
- Understanding: To have understanding is to know how things are connected together. The more connections you grasp, and the more fundamental and important those connections, the better your understanding. Because of #1 (maximal scope) and #2 (perfect accuracy), perfect, divine knowledge entails perfect understanding. In the words of Wilfrid Sellars, it entails understanding “how things, in the broadest possible sense of the term, hang together, in the broadest possible sense of the term.” In short, God understands perfectly how everything is connected to everything else.
- Articulation: Animal knowledge and most causal human knowledge is inarticulate. Expert human knowledge is considerably more articulate, but even there, as Michael Polanyi has shown, much of our knowledge necessarily remains “tacit.” What we know explicitly, with articulation, we know only in relation to a larger background context that, as background, remains tacit or unarticulated. The reason for this is because articulate human knowledge is abstractive. It is “drawn out of” (that’s what ‘abstract’ literally means) a richer, more concrete experience. And the reason our articulate knowledge is abstractive is because, as finite, localized beings, we necessarily approach reality from a situated vantage point and because, as embodied beings, we can only process so much information at a time. Thus, even though our experience at each moment is a whole, a Gestalt, it affords us only a partial, fleeting glimpse of a much larger reality and presents too much information for us to process as a whole. To understand it, we have to analyze it, to break it down. We cannot truly focus on more than a small experiential “chunk” at a time, and we cannot articulate that upon which we cannot focus. But perfect, divine knowledge does not have these limitations. Because God’s knowledge has maximum scope (#1) and immediacy (#4) and because God’s reasoning isn’t constrained by a finite processing speed, God’s knowledge isn’t abstractive. Consequently, there is for God no distinction between focal, articulate knowledge and background, tacit knowledge. The Gestalt of God’s experience is originally and fully articulate without first needing to be broken down into “bite-sized” analytic or propositional chunks.
- Security (objective certainty): With few exceptions (e.g., blindingly obvious conceptual truths like 1+1=2), human knowledge is fallible. We can be and often are mistaken. We often think we know things that we don’t actually know. In contrast, knowledge with maximal scope (#1) and perfect accuracy (#2) is infallible. It is perfectly secure. It cannot be mistaken because there’s nothing outside the scope of that knowledge to contradict or undermine it and because perfect accuracy means there’s no imprecision that introduces error.
- Credence (subjective certainty): Because most of our knowledge is fallible, our degree of confidence or credence in what we (think we) know is variable. Sometimes our credence is very high because the evidence supporting our knowledge claims seems utterly conclusive. Other times our credence is much lower because we realize that our evidence is limited and imperfect. In contrast, because perfect, divine knowledge is objectively certain or infallible (#8) and because God perfectly knows that His knowledge is such (#5), whatever He knows He knows with maximal credence. He always has maximal confidence.
Side note: The Bible has many passages were God is seemingly presented as speaking with less-than-maximal credence. For example, in Jer. 26:3 and 36:3 God says “perhaps” the Israelites will turn from their wicked ways. Furthermore, there are hundreds of verses where God speaks in conditional (if–then) terms, e.g., 2 Chron. 7:14. In many instances these conditionals can be read in a way that suggests God is uncertain how things will play out. Are these passages counterexamples to #9? No. The claim there is that whatever God knows He knows with maximal credence. The claim is not that whatever possibilities God considers are known with maximal credence. These passages only become problematic for #9 if we assume that the future is exhaustively and objectively settled, in which case God should know with absolute confidence exactly how the future is going to go. If that were the case, then we shouldn’t expect to see any expressions of divine uncertainty in the Bible. But if the future is, as open theists like myself believe, objectively open-ended, then a perfectly knowing God knows that there is no exhaustively settled future. So, when God says “perhaps” or conveys uncertainty with “if,” that’s because God knows with maximal credence that there is no objective certainty in the matter for Himself or anyone else to know.
6. Conclusion
I have now significantly unpacked Ofull. To say that God is omniscient, in the full sense of that term, is much more than to say that God knows all true propositions and believes no false ones. It is to say that God knows all of reality as well as it can possibly be known, meaning that God knows all of reality (maximal scope) with 100% accuracy, retention, and immediacy, with complete understanding, articulation, security, and confidence, and with reflexive transparency. Everything that is, whether within creation or God Himself, is laid bare before the eyes of God.