Descartes does not re-establish the existence of a physical world until he reaches the Sixth, and last, of his Meditations. His progress through the Meditations, however, is not so much like a straight line as like a spiral: a topic is taken up at an earlier stage of his reﬂections and then left, to be taken up again at a later stage. So it is with physical objects. Before he reaches the ﬁnal point of arguing that they genuinely exist, Descartes has twice addressed himself to the questions of what they must be like if they do exist, and what must be the nature of his understanding of them. The ﬁrst of these discussions is to be found quite early in his progress, in the Second Meditation, and the second – a very brief consideration of the ‘essence of material things’ – is at the beginning of the Fifth Meditation.