What makes a belief justified or reasonable? We think we know many things, but we can’t always explain how we know they are true. Some of these beliefs might be self-evident, some of them are based on experience, some are “successful assumptions,” and others are unjustified prejudice. However, we have little choice but to do philosophy in the face of uncertainty and take certain beliefs as “common sense” before we can conclusively understand how we justify those beliefs.1 This is why philosophy makes such heavy use of what’s intuitive (beliefs that do not seem to be absurd and seem compatible with our knowledge). I currently believe that the most modest form of justification is through the creation of successful assumptions similar to “working hypotheses” and that is all we usually need when we argue within the philosophical tradition. I will describe self-evidence, coherence, experience, working hypotheses, and theoretical virtues.2 I will then explain my current understanding of justification (epistemological theory)—a form of common sense philosophy that I call “theoretical virtue epistemology.”3
The idea that some beliefs are justified because they are self-evident is the idea that some beliefs require no argument for them to be justified. (Self-evident beliefs have a noninferential form of justification.) What we experience (such as our pain) and our mathematical knowledge seems to many to be justified through self-evidence. We are justified to believe that “1+1=2” is true and we are justified to believe we are in pain or see green when we have certain experiences. Robert Audi argues that self-evidence often requires a certain degree of wisdom and contemplation.
Coherence is the main alternative to self-evidence. If a belief can’t be justified through self-evidence or some relation to other self-evident beliefs, then many will argue that the belief can be justified anyway through its relation to our other beliefs, experiences, and “knowledge.”4 For example, I see my hands and I think my belief that I have two hands is justified. I might be in some deceptive dream world and actually just be a brain in a jar. At the same time I know that I have two hands if my belief is true. Knowledge doesn’t require certainty, it just requires that a belief is appropriately justified.
Why am I justified to believe I have two hands? Because I see my hands, because I think I understand that my eyes are a reliable source of information given my past experiences, and because my assumptions about my hands (they are solid and can touch things) is confirmed by my experiences of them. You could say that I have a hypothesis that I have hands, that the hypothesis is testable, the hypothesis has been confirmed many times, and the hypothesis has never been disconfirmed. My experiences and my hypothesis are coherent because they are logically compatible. My experiences and my hypothesis could both be true. The more risky predictions a hypothesis can successfully make, the more likely it is that the hypothesis is true. My hypothesis that I have hands must also be justified in terms of alternative hypotheses, but it seems to be the “best explanation” for my experiences.
Coherence theorists don’t necessarily think all of our beliefs must cohere with our experiences. I think I am justified at believing that I’m not currently in a dream world despite the fact that all my experiences would be the same in that dream world (and it’s certainly not self-evident that I’m not in a dream world). The assumption that I’m not in a dream world is at least partially based on the fact that it coheres the assumption that dreams tend not to make a lot of sense. However, it might be even more important that the assumption that I am in a dream world lacks certain theoretical virtues. (I will discuss that issue later.)
It should be noted that justification through coherence must be sophisticated, and we might even have to reject coherence from time to time. My belief that “1+1=2” could be incoherent with my observations about the world, but that would imply that my observations about the world are wrong and not the other way around. We are simply more certain that mathematics is reliable than we are certain that our observations are reliable. However, it’s always possible to be forced to accept two contradictory beliefs that are both highly justified when we have no way to reject one of them. Perhaps we might be forced to accept two incompatible mathematical truths at some point until we can resolve where the error in reasoning took place.
We take our experiences to be important because it’s an outside source of information. If we only justify a belief through its coherence with our other beliefs, then there’s a higher chance that the belief is merely prejudice. For example, people who think they are in a dream world have no way to support or correct that belief through experience. On the other hand, beliefs that are based on experience tend to be testable through risky predictions.
A working hypotheses is a proposed explanation for a phenomena that may or may not have been tested. A working hypothesis that has been tested and confirmed (rather than refuted) becomes more and more justified based on its success. A working hypothesis should be coherent with our current knowledge, but it is often necessary to test our “common sense” assumptions.
Theoretical virtues are the various forms of justification. Although self-evidence, experience, and coherence are three important forms of justification, there are others. For example, logical coherence, predictability, comprehensiveness, and simplicity. Our observations are more likely accurate when they confirm risky prediction. Our “coherent” beliefs can be logically compatible with our other beliefs, but they can also be “comprehensive” in proportion to the number of beliefs they cohere with. Additionally, an explanation is justified to the extent that it makes predictions and is comprehensive by explaining many of our beliefs or experiences rather than few.5 Given two beliefs we should also prefer the simpler one—and that is one of the best reasons to reject the belief that I am in a dream world. If I am in the real world, then I exist because I have a body and my observations are reliable because I have sense organs. However, if I am in a dream world, then we are in serious need of an explanation—what is causing the dream? Am I just in bed, or is there a super computer causing the dream? In that case we must posit the existence of both a dream world and a nondream world.6 That is unnecessarily complected and more ambitious than the modest belief that I am usually in the real world.
My Current Thoughts on Justification
I don’t have any strong beliefs concerning coherence or self-evidence. The problem is that what we think we know intuitively is merely difficult to explain in words, but the actual argument for an intuitive belief could involve any of the theoretical virtues—and it’s not clear to me that self-evidence, coherence, or experience are separable from the other theoretical virtues that I mentioned. (I’m not even sure if any of our beliefs are actually self-evident.) In fact, some beliefs seem like they are highly justified despite not being self-evident or something we can prove through experience. Such beliefs are much like working hypotheses except they might not always be explanations.
For example, we are not certain that the future will be at all like the past (because the laws of nature will be the same), but we think we know that tomorrow will be much like today—the sun will rise in the morning, people will still buy things with money, bread will still be nutritious, and so on. I don’t see how we can know anything about the future through self-evidence or experience. What we experienced throughout our lives tells us nothing about what the future will be like.
How do we know that the future will be like the past? Because it’s a successful explanation both compatible with our various beliefs and able to comprehensively explain those beliefs. It’s common knowledge that the sun will rise tomorrow, and the assumption that the future tends to be like the past explains that knowledge. Additionally, a rejection of the assumption seems absurd. Assuming that the future won’t be like the past because the laws of nature will stay the same makes living our lives impossible. We can’t know to eat bread, to keep lead away from our food, or to save our money.
Our philosophical arguments need not conclusively prove anything to be true once and for all. Instead, we can compare various explanations and beliefs to decide which is the most justified. A working hypothesis tends to be justified if it’s the “best explanation,” and other beliefs tend to be justified if they are the best beliefs compared to the competition. (There might be exceptions where the best explanations are almost certainly false and we should simply admit ignorance.)
My main point is that the way we can justify our belief that the future will be like the past is both modest but perfectly good. We should even say we know the future will be like the past. We don’t always have to concern ourselves with ultimate forms of justification involving self-evidence or observation. Our philosophical beliefs can be perfectly good and reliable despite the fact that they aren’t justified through self-evidence, mathematics, or natural science. Knowledge of the future is a good example of that and science itself depends on the assumption that the ultimate laws of nature will stay the same in the future (and there will be ways to predict if certain laws of nature will change).
If we want to justify a philosophical belief through argument, then we should take a close look at the theoretical virtues and we need not discuss self-evidence. Of course, that doesn’t mean we shouldn’t discuss self-evidence when it proves to illuminate our understanding of reality. If self-evidence exists—That is merely a “deeper” and more ambitious realm of philosophy.
What about people who reject that the laws of nature will stay the same? To reject highly plausible beliefs just because they can’t be known through self-evidence, observation, or proven once and for all in some other way leads to absurdities; and I suspect that there is a common failure in reasoning where a person decides something must be false or unjustified if it can’t be explained. It took me some time to decide how to explain how we know that the laws of nature will stay the same in the future, but that doesn’t mean it was false until I came up with my explanation, and I see no reason to think we can know the laws of nature will stay the same in the future through self-evidence or experience.7 I think this failure in reasoning was committed by David Hume when he decided that there was no reason to think the laws of nature will stay the same in the future, and it is committed by philosophers who decide that the mind as we experience it is an illusion because “only the physical world exists.” The mind as we experience it could be physical.
Some beliefs are so intuitive that denying their truth seems absurd. This is a good reason not to reject the belief. Although some people might claim to deny such highly plausible beliefs, just like Hume denied that we can know that the laws of nature will be the same in the future, we have reason to doubt them. Even a person who explicitly rejects a highly plausible belief might still have other beliefs and behavior that would indicate that the belief is still there, and we can know something is true without being aware of our own knowledge. For example, Hume didn’t know how to explain how we could know that the laws of nature will be the same in the future, so he intellectually decided that he didn’t have such knowledge after all. I think Hume did know the laws of nature would stay the same in the future despite his argument to the contrary.
The reason that I believe in common sense philosophy—what I call “theoretical virtue epistemology” is because I have little understanding about self-evidence and I believe in “common sense justification”—I think we can justify beliefs with theoretical virtues other than observation and self-evidence.8
What are common sense beliefs? I often refer to “common sense beliefs” and I think I use the term quite similar to how other people use it despite my technical understanding—that a belief is common sense insofar as it is intuitive but difficult to justify through argument. Common sense beliefs need not be justified through argument, self-evidence, or observation; but they often can be. Common sense beliefs should be justifiable through some theoretical virtues. Common sense beliefs are often the starting point of philosophy and can be assumed to be true until we have a reason to reject them.
The terms “common knowledge” or “uncontroversial” are not a good way to describe how I view “common sense beliefs” because common sense beliefs need not have a high degree of certainty and need not be something easily understood by people. That’s not to say that common sense beliefs are never common knowledge or uncontroversial.
What is common sense justification? Common sense justification is justification that is neither based on self-evidence nor observation. Instead, it’s a justification based on other theoretical virtues. Such beliefs can be called “assumptions” because they can’t be proven to be true once and for all and they must be compared to alternative beliefs. These are the beliefs that are like “working hypotheses” because they are justified for being the best belief compared to known alternatives, but it’s always possible for even better alternatives to be discovered in the future. For example, I have no reason to believe I am in a dream world at this moment, but new experiences or arguments might change my mind.
What is common sense philosophy? Common sense philosophy includes what I describe as “common sense justification” but need not limit itself to that form of justification. (In fact, I think common sense philosophy must also accept observation as a strong form of evidence.) Self-evidence is compatible with common sense philosophy.
I don’t have a strong opinion about self-evidence, but I endorse common sense philosophy insofar as I accept what I call “common sense justification” and such a modest kind of evidence is often the starting point of philosophy, even though common sense beliefs must occasionally be rejected as “prejudice.”
Modest philosophical arguments need not be justified through self-evidence, experience, mathematics, or natural science. Those forms of justification can be helpful, but modest common sense arguments are often good enough, such as my argument that the future will have the same laws of nature as the past.
3 “Theoretical virtue epistemology” should not be confused with “virtue epistemology,” which discusses intellectual virtues—characteristics of people that make them better at attaining knowledge. My hypothesis mainly concerns positive characteristics of theories, hypotheses, and beliefs rather than people.
4 Here “knowledge” might be better described as “justified beliefs” or “what we believe to be highly plausible beliefs.”
5 A fully comprehensive explanation is “complete” if it can explain all phenomena that it should be able to explain. For example, normative moral theories purport to identify right and wrong behavior, so a complete normative moral theory can identify all right and wrong actions.
6 If I am in a dream world now, then my actual dreams must still be explained as well. The dream-world hypothesis seems like it would have to state that there is a real world, dream world, and dreams within the dream world.
7 The problem of natural laws and predicting the future is known as the “problem of induction” and the solution to the problem is a contentious issue in philosophy despite the fact that we know the laws of nature wills stay the same. We can know something is true before we can agree about how we know it.
8 My understanding of knowledge is neither a form of foundationalism nor empiricism., but it could be considered to be a form of a coherence theory of justification. (Unlike many coherence theorists, I am not against self-evidence, and I am not convinced that coherence is always relevant to our justifications, so I don’t know if it’s appropriate to say that I endorse a coherence theory.)