We cannot have direct experience of cause and effect; it is an inference we make. Induction is no different. It rests on the same premise: that nature will behave as it always has. It is not a logical impossibility that nature change, however. So, Hume posits, we cannot claim to know things through inductive reasoning. He acknowledges that induction is a way that we make knowledge claims, and that we cannot simply do away with it, but he concludes that it is ultimately a fallible means of knowledge acquisition.
Circular reasoning
What Hume identifies is part of a larger critique of induction: namely, that induction exhibits the fallacy of circular reasoning. Circular reasoning, or what Aristotle dubbed “begging the question”, is when a rule or law is only justified through that same rule or law (Aristotle: The Complete Works, 2023). One of the pieces of evidence that is there to support or necessitate the conclusion, relies on the validity of that same conclusion. The process of reasoning is supposed to leave us with a conclusion we know to be true based on the truth of the premises. Looking at deductive reasoning, we can see how the conclusion is necessarily true by virtue of the premise; humans are mortal, Socrates is human, therefore Socrates is mortal. In this type of logic, the premises lead to the conclusion. That’s not to say that deductive reasoning is always valid, but as long as the premises are true, the conclusion will be.
Epistemic circularity, or premise circularity, explains one type of circular reasoning. This type of argument is often considered a fallacy or dilemma because it does not provide us with any certainty. For example, if Megan says she is honest, and you know that Megan doesn’t lie, you are likely to believe that Megan is honest. In order to believe Megan is honest, you have to believe she does not lie, but you have to believe Megan doesn’t lie to conclude she is honest. The premise for this argument relies on the truth of the conclusion, making it circular, and a logical fallacy; it proves nothing.
Many see induction as a process of reasoning that is epistemically circular. In order for induction to provide us with a justified knowledge claim, its true premises must provide a true conclusion. Induction relies on what Hume calls “the principle of the uniformity of nature”; that nature is stable and hence will continue to behave as it has been observed to do so in the past. But we may ask, how do we know that the past will resemble the future? The answer would be that, in the past, those inferences have been correct. If, on Monday I claimed that the sun would rise on Tuesday, and it did, that seems to be justification for using that type of reasoning moving forward. But we see here how the conclusion brings us back to that original question: how do we know that the past will resemble the future? Essentially, we justify induction through inductive reasoning itself. Hume asserted that, when the premise of an argument relies on the truth of the conclusion which, in turn, depends on the premise, it is a circular argument which offers no certainty.
Some types of circular arguments are indeed a logical fallacy. That being said, there is a position that supports circular arguments, claiming they can have logical validity. Another way to look at circular reason is through something called rule circularity. Rule circularity holds that we can in fact use a rule to justify the use of that rule. We don’t necessarily have to know the rule is justified to be justified in using it. As long as the inference allows us to deduce true conclusions using logic – that is, as long as the conclusion asserts something about the premise – we are entitled to make those inferences. An example of rule circularity might look like this: if an argument that reliably leads from true premises to true conclusions is justified, and induction reliably leads from true premises to true conclusions, then induction is justified. We see here how the premises do not depend on the conclusion in the way they do in epistemic circularity – the conclusion is not in the premises – but rather, the premises infer a rule that leads us to a conclusion about that rule.
While epistemic circularity is vicious, thinkers like R. B. Braithwaite (1900–90) hold that rule circularity is unproblematic because the use of the inference has been justified. In The Routledge Companion to Epistemology, Alexander Bird explains the way that rule circularity functions using “R” to represent the rule of induction:
