Assess Rationalism. In this essay I intend to seek the true values of Rationalism through analysing its key concepts.

Another concept of which numerous philosophers conclude we have innate ideas for is Numbers. This idea goes back to ancient Greece where Plato argued that we our concept of numbers are innate on the basis that we never have any sense experience of them. For example, the number two is not something you can encounter with the five senses. We may come across a pair of socks or couple of people but never two itself. It seems that what we experience is merely an example ‘two-ness’ but never the real thing. From this, Plato concluded that this concept must be encounter in a realm of pure thought, independent from the senses.

In response, Empiricists say that we can acquire the concepts of different numbers by abstracting from the experiences of collections of objects in the world. After several encounters with objects in threes I can work out what they have in common. The concept of three is a copy of this common denominator. However this does not explain how we have the concept of number we haven’t encountered. For example, I have the concept of 6,000 but I have not experienced objects in a group of 6,000. However Descartes counters this response by highlighting that we can for images of geometric shapes such as a triangle in our mind’s eye, suggesting that the possibility that our concept of the shapes comes from a sense experience of them copied into an image retained by our minds. Furthermore, Descartes points out that we are capable of understanding the concept of a shape with 1,000 sides even though we have no clear image of the shape in our minds. He concludes that geometric shapes are conceived not in the imagination as a copy of sensations but rather by the intellect. This supports Plato and Rationalism whereby Descartes argues that we can grasp number and shapes without the use of senses but through an innate idea.

Another fundamental aspect of Rationalism is distinguishing between a priori truths and a posteriori truths. Truths that can be known without experience or the use of the senses are a priori, whereas truths that can only be known via the senses and through experience are termed a posteriori. Furthermore you can tell that some truths are known simply through examining the meanings of the terms involved. These truths are analytic. In contrast, truths which are not true simply by definition and can be denied without contradiction are labelled synthetic. However, it is the a priori truths that very much interested Plato. Plato insisted that knowledge had to involve self-evidence and this possibility is satisfied most successfully by beliefs obtained a priori. What makes this so appealing, especially regarding mathematical truths, is that once we see its truth we recognize that no further evidence could undermine it. It is a truth which we cannot change and it is a truth which could not be otherwise.

Plato strengthens this argument with the Meno. After we understand the proof of the Meno, we identify it to be true for all squares, not just that of the diagram. From this, Plato gathered that such knowledge could not be derived from experience as our experience is only of certain squares not all squares. Plato concludes that the mind sees the form of the square and recognises truths about this rather than about a particular square we see. From this he thought that we have an innate ability which recognises such truths as eternal and necessary. This then supplies us with genuine knowledge.

Descartes deemed it to be possible to work out physical laws and mathematical certainty without any empirical experience but solely reasoning from indubitable first principles. However he came across a hurdle when attempting to move from knowledge of his own experience and of a priori truths to knowledge of the physical world. Therefore the argument goes that mathematical truths may be eternal but cannot be used to tell us how the world behaves. For example to add three marbles to four marbles may tell us that we have seven marbles but it cannot tell us anything about marbles themselves. This implies to anti-rationalists that the cost of saying that knowledge comes through reason seems to be that we end up not knowing much at all.

Overall, I think Rationalism is a reliable source of knowledge is backed by pure reasoning. It is only with pure reasoning, I believe, that we can come to acquire genuine knowledge as pure reason is not subject to doubt or deception. Therefore we can trust our self that our reasoning is correct.