Category Archives: epistemology

What is knowledge, and how can we acquire it?


Sometimes people are inclined to describe an area of inquiry, like morality, as subjective. However, it is important to separate out two senses of the word “subjective,” which I will call the metaphysical sense and the epistemological sense.

  • An area is metaphysically subjective if there actually are no objective criteria for deciding questions in that area of inquiry.
  • An area is epistemologically subjective if there are objective criteria for deciding questions in that area, but we don’t know what they are.

Every area of inquiry is epistemologically subjective prior to discovering the objectively correct criteria to employ, by definition. For example, logic was epistemologically subjective prior to Aristotle, since no one had explicit rules for how to reason properly or identify logical fallacies. People just reasoned using intuition until the objective logical standards were discovered.

Some areas of inquiry are metaphysically subjective, like astrology. There are no objective criteria for what your horoscope should say, because the field has no basis in reality. If the objective criteria for an area of inquiry are not known, then that may be used as an argument for the position that that area of inquiry is metaphysically subjective – that is, that there are in fact no such criteria. This is the basis for the philosophical position that morality is subjective.

It is critically important that we not rest content with a subjective approach to any legitimate area of inquiry, but rather work to define objective standards for everything we do. In the absence of objective standards, disagreement will proliferate, and skepticism and mysticism will run rampant.

Plato’s Dialectic

Plato held that in philosophy, we arrive at the truth by means of a process of “dialectic.” Dialectic, for Plato, works as follows:

  • We begin by having one person put forward an answer to the problem in question on the basis of certain arguments.
  • Another person then comes along, points out flaws in the first person’s answer, and puts forward his own answer.
  • Then a third person comes along, criticizes both viewpoints, and puts forward an answer that is better than either of them.
  • etc.

Plato held that, over time, this process leads us closer and closer to the truth. This is illustrated by some of his dialogues.

Plato’s theory assumes that we have a way of rationally evaluating an answer to a philosophical question as plausible or implausible. Plato held that we could see this “intuitively,” but his account of intuition depends on his metaphysics, which most philosophers have rejected.

Another perspective on dialectic comes from David Hume. Hume agrees that it often happens in philosophy that one person puts a position forward, and then another person criticizes it and puts their own position forward. However, according to Hume, the intuitions that this process depends on are subjective products of “habit or custom.” So, while dialectic can arrive at conclusions that better appeal to a given person subjectively, it is not a source of objective truth like Plato thought.

I think the only way to answer Hume once and for all is to present a body of demonstrably true conclusions in philosophy. So long as philosophy is seen as an endless debate, many will be inclined to question whether it has any cognitive status at all. There have been a number of attempts to do this since Hume, and evaluating all of them is beyond my scope here.

In Defense of Self Evidence

A self evident proposition is a proposition that any rational person will agree is certainly true upon grasping it. In this post, I will demonstrate that there are self evident propositions.

The strongest argument for the claim that there are self evident propositions is to just list several of them so that the reader can see that some propositions are really self evident. Here are three:

  • There is an objective reality.
  • A thing is identical to itself.
  • I am conscious.

I will explain each of these.

“There is an objective reality” means that there is a fact of the matter about something. For example, if I say that we landed on the Moon, and someone else denies that we landed on the Moon, there is a fact of the matter about which of us is right. The fact of the matter about whether we landed on the Moon is one component of the objective reality in which we live.

The existence of an objective reality is contained in every experience we have. When I experience the fact that my alarm clock is red, I can see immediately that my alarm clock really exists, that it really has certain properties like redness, and that its existence and properties are independent of my mind. This experience shows me directly that there is an objective reality.

“A thing is identical to itself” means that a thing is what it is. A tree is a tree, and has all of the properties required for being a tree. Symbolically, this is often expressed “A is A,” where A refers to anything that exists.

This proposition, called the law of identity, is contained in every thought and every observation we have. When you observe a computer, you also observe that that computer is a computer. When you think of the number one, you can see that the number one is the number one. This is one of the undeniable foundations of rational thought.

“I am conscious” means that I am aware of the world and can identify things that exist using my mind. I can perceive the things that exist, whether they be cars, animals, or anything else that is presented to my senses. I am actually aware of the world.

Obviously, the fact that we are conscious is forced upon us by every perception or thought we have. If I perceive a lamp, I can see that I am aware of that lamp. If I think about Nazi Germany, I can see that my mind is thinking about Nazi Germany. Every act of my consciousness contains consciousness. Thought and perception are undeniable data of experience.


Having gone through these examples of self evident propositions, we can see that there are in fact self evident propositions, since there can be no doubt about the existence of an objective reality, the law of identity, or consciousness.

Some philosophers have raised objections to the idea of the self evident, and I may address those objections in another post. Keep in mind, though, that even if we do not know the answer to some tricky objection, that casts no doubt on the idea of self evidence or the self evident propositions I have enumerated. We can see, just by looking at them, that any objection to these propositions has to fail, even if we cannot identify the error in a specific objection.

Disjunctive Syllogism

The disjunctive syllogism is a form of deductive reasoning that goes as follows:

  1. Either p is true, or q is true.
  2. p is false.
  3. Therefore, q is true.

This is a deductively valid form of reasoning because, given that p and q are the only alternatives, and p is false, q has to be true. The conclusion follows necessarily from the premises in virtue of the form of the argument.

This form of reasoning is useful when we have a small set of hypotheses, because we can use it to narrow down which one is true. For example, in a murder trial, we might know that the only people at the scene of the crime were Alex and Bob. So, we could reason as follows.

  1. The murderer was either Alex or Bob.
  2. Alex is on video camera in a different room at the time of the murder, so he can’t be the murderer.
  3. Therefore, the murderer was Bob.

Importantly, this requires us to actually have a good reason to believe that Alex and Bob were the only people at the scene of the crime. If there is evidence that there might have been a third person at the scene of the crime, then our argument commits the fallacy of the false dichotomy, because there is a third possibility, namely that the murderer was this third person. This may create “reasonable doubt” in the jury’s mind about whether Bob was the murderer, depending on the other facts.

However, alternative hypotheses cannot be generated arbitrarily. There has to be some reason to take a hypothesis seriously before it becomes an objection to our argument. For example, the defense attorney can’t say “maybe a Martian was the murderer” – that is a doubt, but it is not a reasonable one, and so does not undermine our argument.

Objective Definitions

I was asked on another website how we should treat definitions that aren’t strictly convertible with the concepts that they define. In other words, in mathematics and logic, you can generally just substitute a concept whenever its definition appears, because there is nothing more to the concept than its definition states. You can’t do that with a lot of definitions elsewhere. For example, a horse without hooves is still a horse even though it doesn’t strictly meet the definition of a horse.

However, even when we define a term in mathematics, we don’t generally do so as an end in itself, and if we did our definition would quickly be forgotten or discarded. We formulate our definitions in order to prove things from them. The definition names a useful starting point in our reasoning for seeking out and identifying logical connections that exist objectively.

So, on the view I’m defending, our main goal when we define something isn’t necessarily to come up with a definition in which the subject is strictly convertible with the predicate, it is to identify the essence of the subject. This is a true proposition, in genus and differentia, from which the most of the subject’s known attributes follow, whether causally or logically. If the definition is convertible with the concept it defines, great, but if not, that’s fine too.

So, when we’re defining, say, a horse, the goal shouldn’t be to come up with a proposition that’s true of every horse, although it would be great if we could. We want to find the essence, a proposition which identifies the genus and differentia from which the most of the attributes of horses follow. We want the definition to do this because it will enable us to draw the most true generalizations about horses in our subsequent research, although we may have to take particular exceptions like the occasional horse without hooves into account when we are reasoning about them specifically.

Putting God on Trial

A lot of atheists hold that although they don’t have any evidence that God exists, and therefore don’t believe in God, he might exist. It’s just very unlikely.

One of the atheists who hold this position is Matt Dillahunty, who compares the atheist’s position on God’s existence to a trial verdict. In a trial, the defendant is not found to be innocent, they are found “not guilty” – meaning that there wasn’t enough evidence to convict them of a crime. Analogously, according to Dillahunty, the atheist is not finding God innocent of existing, i.e., concluding that God does not exist. Rather, he is finding God “not guilty” of existing, meaning that there isn’t enough evidence to conclude that God exists.

I agree that there isn’t any good evidence for God’s existence, but the conclusion Dillahunty draws is not the correct one.

I like the analogy to a trial, so I’ll stick with that. Before a trial is held, there is a preliminary hearing to determine whether there is enough evidence to warrant even having a trial, which is a lengthy and laborious affair. Similarly, before considering a position, it is necessary to have some evidence indicating that it might be true, and is worth investing one’s limited time and energy in exploring further. Positions that fail this initial inspection are “arbitrary.”

Once we have concluded that a position is arbitrary, there is no need to consider it further. We are not obligated to assign it some “degree of probability,” since it has no relation to our knowledge, and hence there is no basis for such a probability assignment. Nor are we obligated to say that it is “possible” or “might be true.” A claim is possible, epistemically, if there are some facts in its favor, but there are no facts in favor of a claim if it is just an arbitrary assertion.

The correct position for an atheist to hold on God’s existence isn’t “it’s very unlikely, but it might be true,” it is “I have no reason to consider that idea.”

Science and Philosophy

In an earlier post, I argued that neuroscience was relevant to philosophy of mind, because neuroscience provided support for the claim that the brain is not unified in the sense that consciousness is, which is an important claim in philosophy of mind (see the post for elaboration).

I have reconsidered this, because it occurred to me after a discussion with one of my professors that we don’t need neuroscience to know that the brain is not unified like consciousness is. Anyone can see, from the most elementary, pre-scientific knowledge of what the brain is, that the brain is not indivisible. You can’t have half of a mind, but you can have half of a brain.

This is part of a consistent pattern I have observed. Scientific experiments which claim to contribute to philosophical debates always, in my experience, end up falling into one of two traps:

  1. Triviality: The philosophical point the scientific experiment attempts to prove could be argued for equally well from pre-scientific knowledge.
  2. Ambiguity: The scientific experiment can be re-interpreted by opponents of the philosophical claim it attempts to prove.

I’ve yet to see a scientific experiment that didn’t fall into one of these two traps. However good it may be as science, when it is interpreted as an argument for or against a philosophical position it always turns out to be trivial or ambiguous.

This is not to say that you can’t make it easier or harder to hold a philosophical position using science. I would say that scientific discoveries like the theory of evolution have made it harder – not impossible, but harder – to believe in God. I do not mean to say that there is a deductive argument for atheism here, but familiarity with the theory of evolution could give a person the sense that the world is entirely explicable naturalistically, or knock out primitive forms of the teleological argument that formerly served as a basis for faith.