Medieval Epistemology: Rationalism and Empiricism in the 12th Century

1.1 Knowledge Problem: Rationalism and Empiricism

The central concern of philosophy was the problem of knowledge. Rationalism and empiricism faced the same problem, but differed in how to approach and address it. Rationalism is characterized by the primacy given to reason in the pursuit of truth, and its basic principle is that our true knowledge of reality has its origin and basis in reason. Rationalists identify rational knowledge with scientific knowledge, especially mathematics. They are therefore convinced that the structure of reality is mathematical in nature and believe that mathematics is the only path to certain knowledge of reality. The problem, then, is to develop the method of applying mathematics to philosophy: a deductive system. Deduction is an argument that reaches a necessary conclusion from some general propositions; if these are true, the conclusion will also be true. Another problem is to establish the origin of these ideas.

Empiricists hold that our knowledge comes from the senses, that the origin of our knowledge is sensory experience. This sets a limit to the possibilities of knowledge: it cannot go beyond experience. Any knowledge will be rejected if it cannot be reduced to the field of the senses. They reject the innate ideas posited by rationalism, and the method they advocate is induction, as opposed to deduction: reasoning from particular experiences to extract universal conclusions.

2.1 Modes of Human Knowledge and Method

According to Descartes, there are two ways of knowing by reason: intuition and deduction. Intuition is a kind of natural light through which we grasp immediately, and without any possibility of doubt or error, simple and true ideas, because they are self-evident. These are clear and distinct ideas, also called simple natures, from which knowledge is developed through deduction, the second mode of knowing, which is defined as any necessary inference from other facts that are known with certainty. Intelligence discovers connections between the different intuitions and proceeds step by step through deduction. Deductive reasoning is an ordered sequence of evidence. The inspiration is clearly Cartesian mathematics. He considers how to proceed from the properties posited by geometry to advance knowledge in philosophy.

There are three methodological points:

1. Apply the method of geometry and develop a chain of simple and clear reasons.
2. Accept as true nothing that is not clearly certain.
3. Respect the proper order of deduction and proceed from evidence to evidence.