Quelle surprise

John Herve re-assesses Descartes

Most of us are aware of the ‘milestones’ which form our Western world-view. One of these is the works of Rene Descartes (1596–1650).We can probably quote one of his central tenets – ‘I think, therefore I am’. It has ‘centre-stage’ in his philosophy and was the catalyst for the rationalist school of thought; one of the abiding traditions of Western thought. But ‘lurking in the wings’ is a further, often forgotten tenet.

When attention is drawn to this it often produces nothing short of astonishment in theists and non-theists alike. More, the intellectual journey through which his ideas developed was remarkable.


For his starting point was mathematics. He invented a new way of applying algebra to geometry; he also created the graph (indeed, the two main axes are entitled ‘The Cartesian Co-ordinates’). He was enthralled by the totally reliable certitude of the discipline. But, significantly, it led him to ponder upon whether the certitude of mathematical methodology could be applied to other areas of knowledge, to see if there is anything outside mathematics whose truth it is impossible to refute.

He concluded that certainty in mathematics is reached by logical progression; this begins with premises which are utterly simple and obvious and cannot be refuted (e.g. a straight line is the shortest route between two points). But it then moves on, again by simple and obvious steps, to reach conclusions which are not at all simple or obvious! These are all reliably true, and open up a world of great practical usefulness. Now, he asked, can there be any premises outside mathematics from which we can move on to knowledge which is totally certain, reliable and true?

Staged progress

This set him off on three separate but contiguous stages. First he considered human experience – can I trust what I experience as having any reliable form?

Sadly – no! For my senses frequently deceive me. A building appears as a different colour at dawn, in sunlight, at dusk. A branch ‘bends’ in the water. So things are rarely in reality what they appear to me to be.

This led him on, secondly, to pursue the quality and nature of this distorted human experience. Sometimes he experienced doing something in reality which was not real at all. He was in fact dreaming. Yet a dream has all the hallmarks of reality (indeed, in dreams one rarely does un-real things). And how can one be sure one is not dreaming reality at any given moment? From this he moved on to a third stage, asking: what is the origin of this situation?

He concluded that his despair that nothing is reliable and truthful could even result from a malign ‘spirit’ or force (he was a man of his time) whose sole purpose is to deceive and de-stabilize reality. So there can be anything I experience that I can rely on, that I cannot be deceived about?

The ‘penny drops’

After this third stage, he realized he was ‘missing a trick’: that however distorted the reality of the experience, however false the inferences, it is I who have the experience and I who make the inferences. However distorted the reality is, I can be absolutely sure I am experiencing it. Thus there is certainty. I know I am an existing, experiencing being. That is unquestionable. Further, I am conscious (i.e. aware) that I am experiencing whatever it may be. In other words, ‘Cogito ergo sum; I think therefore I am’.

Most people leave it at that. But there is a surprising twist, for Descartes does not leave it there. We have indeed reached the central platform of his ideas, but there is something else.

Having established that there are things I can know for certain outside mathematics (i.e. my own consciousness), he asked, ‘is there anything else I can know for certain’? His answer is arresting. ‘Yes’ he says – the existence of God! How is that? Well, Descartes has concluded he is a conscious being. That conscious awareness tells me I am imperfect, my inferences of reality are fragile, I am perishable, finite and transitory. Yet part of my consciousness is also the concept of a perfect being, eternal, infinite and imperishable.

God must in certitude exist for he has created an awareness of himself within me. I know he exists, is perfect and therefore cannot deceive me about reality. My mind may deceive me but that part of me that apprehends God cannot.

The total picture

My conscious awareness of God and his nature means I can utterly rely on him. God does not deceive. My senses deceive. But that part of me which I irreducibly am, that comprehends God, does not. So the centre-stage ‘Cogito ergo sum’ cannot stand alone; what must follow is ‘Sum Deus est’ (I am, God is). To regard Descartes as acknowledging one without the other is to pervert his entire framework.

Descartes still stands among the giants of philosophy, not only because of his novel approach to the nature of knowledge and the re-working of the ontological argument for God’s existence. For his style is unsurpassed, and his work is written with clarity and jargon-free’. For a rewarding and stimulating introduction to philosophy, try reading his Discourse on Method followed by Meditations. ND

Return to Trushare Home Page

Return to Home Page of This Issue