Justified True Belief (JTB)

(●) The Quest to Define Knowledge
Since the time of Plato, philosophers have debated the nature of propositional knowledge...what it means to truly "know" something. In his dialogue Theaetetus, Plato explored the idea that knowledge might be "true belief with an account," a view that later evolved into the well-known "justified true belief" (JTB) analysis. + "true judgment with an account"...is the closest to what later philosophers called "justified true belief." However, Plato ultimately finds problems with each definition and does not endorse any as a final answer in the dialogue.

(●) The Standard Definition: Justified True Belief (JTB)
The standard definition states that knowledge consists of three essential components: justification, truth, and belief. To say someone knows a proposition (for example, "milk is in the refrigerator") means that three conditions must be met: the proposition must be true, the person must believe it, and the belief must be justified.

(●) Truth as a Necessary Condition
For someone to know something, it must be true. It would be nonsensical to claim that someone knows a falsehood. However, truth alone is not enough for knowledge. There are countless truths that no one knows or has even considered.

(●) Belief as a Necessary Condition
In addition to truth, belief is required. If a person does not believe a proposition, it cannot be said that they know it. However, simply believing something does not make it knowledge, since people can believe many things that are not true.

(●) The Insufficiency of True Belief
Even when a belief is true, that alone does not guarantee knowledge. A person might believe something that happens to be true purely by chance, without any justification. For example, if someone randomly thinks, "It is raining in Moscow right now," and it happens to be true, this is not knowledge...just a lucky guess.

(●) The Role of Justification
What distinguishes knowledge from mere true belief is justification or warrant. Justification means having sufficient evidence, forming beliefs in a reliable way (such as through the senses or expert testimony), and having properly functioning intellectual faculties in a suitable environment. The difference between a true belief and knowledge is that knowledge requires this additional element of justification or warrant.

(●) The Tripartite Analysis
The traditional or standard definition of propositional knowledge can be summarized as follows:
A person S knows that P if and only if:
1. S believes that P.
2. P is true.
3. S is justified in believing that P at the time S believes it.
This tripartite analysis remains a foundational concept in the philosophical study of knowledge.

Plato, Theaetetus, in Plato: Complete Works, ed. John M. Cooper (Hackett, 1997). Moreland, James Porter. Philosophical Foundations for a Christian Worldview. 2nd ed. Downers Grove, IL: Inter-Varsity Press, 2017. Plantinga, Alvin. "Warrant and Accidentally True Belief." Analysis 57, no. 2 (1997): 140–145.

+ The Gettier Problem: You walk into your living room, look at the wall clock, see “3:43,” and form the belief “It’s 3:43.” Under normal circumstances, that’s a reliable way to tell the time, and in this case the belief is in fact true: it *is* 3:43. However, you don’t know that the clock actually stopped exactly 24 hours ago at 3:43 and has been frozen ever since. Had it stopped at 3:17 or 8:02, your “method” (glancing at the clock) would have delivered a false belief. So you have a "justified true belief" that still seems wrong to call “knowledge,” because the truth of your belief is heavily dependent on coincidence.

Alvin Plantinga’s diagnosis: proper function, maxi‑ vs mini‑environment, and warrant. Plantinga agrees that luck is the problem, but he gives a more fine‑grained account of where the luck enters. He says our cognitive faculties (vision, memory, basic reasoning, etc.) have a design plan: when they are functioning properly in the broad kind of world they were made for (call this the "maxi‑environment," our normal Earth‑like world), they tend to produce true beliefs. When those conditions are met, a belief has "warrant": the special positive status that, when present in enough degree, turns true belief into knowledge. However, each particular act of forming a belief also occurs in a much more specific "mini‑environment": not just "on Earth," but “looking at this particular clock, in this particular condition, at this particular moment.” Even inside a good maxi‑environment, some mini‑environments are "epistemically misleading": they are such that, given that very specific setup, your properly functioning faculties cannot be relied on to produce a true belief. Now compare two mini‑environments that share the same maxi‑environment and the same cognitive functioning: (1) the clock is working normally, and (2) the clock is stopped at 3:43. In both, you use the same cognitive process by glancing at the clock and reading the time. In (1), that process is 'reliably truth‑producing' in that mini‑environment: in nearby situations just like it (if you looked again, if you came in a minute earlier or later, etc.), the same method would very likely yield a true belief. So here your belief is not only justified and true; it also has a 'degree of warrant high enough' to qualify as knowledge. In (2), by contrast, the mini‑environment is misleading: in nearby situations where you use the same method on that same stopped clock, you mostly get false beliefs about the time. Plantinga’s added "Resolution Condition" says that in such a misleading mini‑environment your belief cannot have warrant in the degree required for knowledge, even if it happens to turn out true once. Thus, on his revised view, the same everyday method (checking a clock) yields 'knowledge' when the local environment supports its reliability, and yields only 'lucky true belief' when the local environment is epistemically hostile...even though your inner mental life may look the same in both cases. See also: • Philosophy / Epistemology: Warrant

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