Rationalism versus empiricism

Rationalists generally develop their view in two ways. First, they argue that there are cases where the content of our concepts or knowledge outstrips the information that sense experience can provide. Second, they constuct accounts of how reason in some form or other provides that additional information about the world. Empiricists present complementary lines of thought.

First, they develop accounts of how experience provides the information that rationalists cite, insofar as we have it in the first place. (Empiricists will at times opt for skepticism as an alternative to rationalism: if experience cannot provide the concepts or knowledge the rationalists cite, then we don't have them.) Second, empiricists attack the rationalists' accounts of how reason is a source of concepts or knowledge.

1. Introduction
The dispute between rationalism and empiricism takes places within epistemology, the branch of philosophy devoted to studying the nature, sources and limits of knowledge. The defining questions of epistemology include the following.

1.What is the nature of propositional knowledge, knowledge that a particular proposition about the world is true?
Knowing a particular proposition requires both that we believe it and that it be true, but it also clearly requires something more, something that distinguishes knowledge from a lucky guess. Let's call this additional element 'warrant'. A good deal of philosophical work has been invested in trying to determine the nature of this additional element.

2.How can we gain knowledge?
We can form true beliefs just by making some lucky guesses. How we can gain warranted beliefs is unclear. Moreover, to know the world, we must think about it, and it is not clear how we gain the concepts we use in thought or what assurance, if any, we have that the ways in which we divide up the world using our concepts correspond to divisions that actually exist.

3.What are the limits of our knowledge?
Some aspects of the world may be within the limits of our thought but beyond the limits of our knowledge; faced with competing descriptions of them, we cannot know which description is true. Some aspects of the world may even be beyond the limits of our thought, so that we cannot form intelligible descriptions of them, let alone know that a particular description is true.

The disagreement between rationalists and empiricists primarily concerns the second question, regarding the sources of our concepts and knowledge. In some instances, their disagreement on this topic leads them to give conflicting responses to the other questions as well. They may disagree over the nature of warrant or about the limits of our thought and knowledge. Our focus here will be on the competing rationalist and empiricist responses to the second question.

1.1 Rationalism
To be a rationalist is to adopt at least one of three claims. The Intuition/Deduction thesis concerns how we become warranted in believing propositions in a particular subject area.
The Intuition/Deduction Thesis: Some propositions in a particular subject area, S, are knowable by us by intuition alone; still others are knowable by being deduced from intuited propositions.

Intuition is a form of rational insight. Intellectually grasping a proposition, we just "see" it to be true in such a way as to form a true, warranted belief in it. Deduction is a process in which we derive conclusions from intuited premises through valid arguments, ones in which the conclusion must be true if the premises are true.

We intuit, for example, that the number three is prime and that it is greater than two. We then deduce from this knowledge that there is a prime number greater than two. Intuition and deduction thus provide us with knowledge a priori, which is to say knowledge gained independently of sense experience.