   The second enters into Reid's development of a consistent geometry for visible space, perhaps the most technically brilliant piece of writing by any major British empiricist. This work allows Reid a crucial reply to advocates of representational theories. Reid discovered and mathematically described a law-like variation in the visible figure of an external object with intrinsic (shape, size) and extrinsic (distance, angle of orientation) properties of the tangible figure. Reid summarizes his conclusion writing: 