The standard definition of rationalism is that a rationalist believes that humans have innate knowledge(concept) or ability to intuit/deduct.

Correct me if I'm wrong, but I think according to the above definition, all philosophers, including empiricists, are rationalists. For example, Locke said that human minds use simple sensory ideas to construct complex ideas. But the very fact that the human mind is capable of such construction implies that the human mind is equipped with at least some form of innate knowledge.

Following this line of reasoning, even the most radical empiricists are rationalists. Experience is a physical, sensory data. Knowledge is an abstract, mental statement. The two are qualitatively different. To claim that we can make a leap from experience to knowledge implies that our mind has the innate ability to deduce one from another.

Is my view on rationalism too wide? Or if it is the case that some philosophers completely neglect the idea of innate knowledge, what arguments does he/she give instead?

  • Considered in such way, rationalists are empiricists and vice versa. Both are not absolutely exclusive. Moreover, rationalism is the approach proposing that knowledge comes mainly from reason, and the equivalent for empiricism. Although Locke is considered one of the most remarkable empiricists, even Kant attributes him the idea of a priori knowledge. See plato.stanford.edu/entries/rationalism-empiricism.
    – RodolfoAP
    Jul 30, 2021 at 7:55
  • @RodolfoAP, It isn't the case that rationalists think knowledge comes mainly from reason. I don't know of any modern rationalist who doesn't think most of our knowledge of the natural world comes from empirical data. Jul 30, 2021 at 23:59

3 Answers 3


"Rationalist" and "empiricist" are technical terms in philosophy, and they don't mean what you might think they mean based on common usage of the words "rational" and "empirical". The SEP puts it like this:

Rationalists claim that there are significant ways in which our concepts and knowledge are gained independently of sense experience. Empiricists claim that sense experience is the ultimate source of all our concepts and knowledge.

Two important things to note about this definition: it doesn't imply that rationalists in any way disregard empirical research, and it doesn't imply that empiricists are in any way not rational. The difference is strictly a question about how we know things about the natural world that we apparently didn't get from our senses.

For example, I ask you how many people will be at dinner and you say eleven, so I set eleven places at the table. I know that there will be one place setting for each diner and one diner for each place setting even before most of the diners have yet to show up. How do I know this? I've never before seen a dinner table with eleven places or eleven diners, and even if I had, I wouldn't be able to identify it because I can't recognize numbers higher than three or four without counting.

You might answer, "Well, the answer is that you counted", but that was a purely mental process; it wasn't a sense impression; it was something that I did in my mind. So how do I know that something I did in my mind rather than experienced in my senses is going to tell me something true about the natural world? A rationalist would say that mathematics is rational knowledge that comes to the mind from some source other than observation. An empiricist would reject this answer.

Before the late nineteenth century, an empiricist would answer that mathematical knowledge is in fact empirical knowledge that we get from sense impressions. They had some rather far-fetched explanations for how this could be. Then along came a philosopher/mathematician named Gottlob Frege who offered another explanation: mathematical knowledge isn't actually knowledge; it's pure logic.

As I said earlier, empiricists are not irrational. They don't (in general) reject logical laws like the law of the excluded middle or modes ponens. So if they can prove that mathematics is nothing more than a sophisticated application of logic, then that solves their problem with mathematics, and there is no need for some other source of information about the rational world.

However, as the question points out, we need some form of innate knowledge just to make sense of sense data. Consider for example, language. How does a baby know that consonants are relevant to meaning, but the differences between his father's voice and his mother's voice are not relevant to meaning? Empirical research indicates that human beings have built-in mechanisms to understand language. You couldn't make up just any random language with any random set of vocalization because the human mechanism for recognizing language expects certain rules to be followed.

Even more fundamentally, empirical decision making depends on recognizing when two objects or two situations are similar and when they are not. How do we recognize this? There is something built in to our sensory apparatus and our brain that makes these judgements for us. Even more fundamental than that, how do we recognize objects? How do we recognize that the apple hanging from the tree branch is a distinct object which can be considered separately from the entire tree? Again, it's something built in to our brains.

However, it might be worth making a note about philosophical tradition. One does not describe this problem by saying that empiricists must be rationalists because that is rather insulting, and philosophical arguments should be rational and temperate. Instead, one says that these issues are problems for empiricism, or reasons that empiricism cannot be true. This is more polite; it doesn't say, "You don't even know what you believe!" it says, "Here's a problem for you, how would you answer it?"


Following this line of reasoning, even the most radical empiricists are rationalists.

Not necessarily! One reasonably well-known empiricist school of thought is Behaviourism, which holds that:

  1. The individual is an Agent, characterised in terms of their actions (e.g. reflexes and stimuli response) rather than their reasons.
  2. Agents learn to act through conditioning, rather than understanding or internal systems.

This allows for positions like the Churchland/Dennett/Rosenberg Eliminative Materialism, where we basically take the mind and mental states or cognitive propositions out of the picture entirely.

  • This is an interesting philosophical stance, thank you for letting me know. I did accept another answer as it was a more general answer but nonetheless I really appreciated your answer!
    – Dimen
    Jul 30, 2021 at 13:44

I mean, you seem to be demanding a rational explanation from a radical empiricist for how humans can take sensory data and do with it everything that we do: claims of truth or knowledge, or moreover abstract reasoning, language, art, etc. Their position sort of excludes the possibility of an explanation for that. This checks out: recognizing the broad brush we are holding, in general, scientists are radical empiricists, and they limit themselves to demanding rational, falsifiable explanations for how/why things happen. Explanations of higher-order human abilities are currently beyond scientific consensus.

Thus, empiricists can be and are rationalists -- the two are not mutually exclusive. The difference is, rationalists claim that ultimately there are rational explanations for those higher-order human abilities, or in the most extreme cases, rational explanations for everything; Empiricists don't wade into those waters, because they're more careful about what they claim is true. Scientists as empiricists totally neglect innate human knowledge, and they call that being "objective" (that is, they are trying to remove their own human subjectivity from the process of science).

Empiricist philosophers, on the other hand, do need to give some account of what's going on in the human skull, but it need not be a rational account. God could be invoked, or the philosopher could simply admit that they do not know, and go on less rational and more empirical endeavors.

  • I'm sorry, but this answer shows no knowledge of the philosophical literature and contains many claims that are clearly wrong: that in general, scientists are radical empiricists, that empiricists can be rationalists (empiricist basically means, "not a rationalist"), your descriptions of both rationalism and empiricism, that neglecting innate knowledge is called "being objective", and the claim that empiricists don't need their accounts to be rational. You are trying to do philosophy based on informal usage of terms that are technical terms in philosophy. Jul 31, 2021 at 0:06

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