Descartes

Descartes opens the First Meditation asserting the need "to demolish everything completely and start again right from the foundations" (AT 7:17). In the architectural analogy, we can think of bulldozers as the ground clearing tools of demolition. For Knowledge building, Descartes construes sceptical doubts as the ground clearing tools of epistemic demolition. Bulldozers undermine literal ground; doubt undermines epistemic grounds.

Descartes' ultimate aims, however, are constructive. Unlike "the sceptics, who doubt only for the sake of doubting," Descartes aims "to reach certainty

Attacking the underlying assumptions of his former beliefs, he asserts that

everything he knew in the past was based upon sense perception. The senses,

however, may be deceptive in that the minute objects are apprehended they may

appear differently from various points of view. It is highly probable that

other things which appear certain through sensation may in reality be the

products of illusions.

Yet there are some objects of sensations which must be accepted as true.

For instance, Descartes affirms that he is seated by the fire clothed in a

winter dressing gown. It would be insane to deny his knowledge of his own

body. We must admit certain characteristics of objects. For instance,

extension, figure, quantity, number, place, time, may be imputed to objects.

In addition, there are mathematical truths relative to objects. We know a

square has four sides and not five. In order to build a valid structure of knowledge he affirms that

he will consider all external reality as