In an article in Mind (Vol. 73, No. 291, July 1964) I tried to show that there is a fundamental difference between primary and secondary qualities. The present analysis of perceived size of an object and its relation to the size of the 'objective' and the 'real' object reveals that my thesis 1 regarding visual primary qualities, viz. size and shape, while true so far as shape is concerned, has to be modified in regard to size. After having criticized the (...) usual view of size constancy, I show by means of a diagram how we may determine the location in physical space of a percept of an object. This diagram reveals at the same time how perceived size decreases gradually with increasing distance of the object from the percipient, but at a much smaller rate than the retinal image of the object. By means of the diagram I show furthermore how the perceived size may in theory vary from person to person. In conclusion a modification of my thesis 1 is suggested. (shrink)