 Like Thomas Reid, who some ten years later also set about investigating what each of the senses can lead us to learn, Condillac took the tactile sensation of solidity to be crucial for the development of an awareness of space and of external objects. Only whereas Reid maintained that we are innately so constituted as to understand the purely qualitative sensation of solidity as sign signifying a quality of external objects, Condillac attempted to explain how experiences of the sensation of solidity could put us in a position to infer that we have spatially extended bodies and that something else exists outside of our bodies (Treatise II.v).