A common criticism of Descartes' theory is that rationalism is not necessary to understand the wax example. Furthermore, the argument goes that only sensory experience can understand the wax example due to the spatio-temporal location of the wax. The empiricist claim of the wax example presupposes the idea that just because the position of the wax is a constant, the wax must also remain a constant. However, this is not the case since without the perception of the nature of the wax it is impossible to formulate the idea that the wax has altered properties but remains the same wax. This is because sensory experience can only recognize the properties of wax. Sensory experience cannot form the conclusion that wax is a constant just because of location as well as being stretchable, flexible and changeable. It is also evident that the liquid version of the wax expands and does not have a fixed shape. Therefore the empiricist claim is unfounded because to gain knowledge other than the properties of each state of the wax, rationalism is essential to provide insight into the reasoning behind the changing properties of the wax. This is why rationalism is fundamental to understanding wax