In the transcendental aesthetic of Immanuel Kant (1724–1804) in the Critique of Pure Reason (Kritik der reinen Vernunft, A version 1781, B version 1787), what we perceive to be space and time do not actually exist outside of our thought. Geometry and mathematics are abstract representations of space and time which have no basis in the sensory world. As architecture is lineament, geometry and mathematics, it can be inferred that it only exists in thought as a representation of space and time. It can be concluded that architecture itself is an a priori category, projected onto the material or the real, as are space and time. Categories in a priori intuition can be seen to be functions of unconscious thought, thus architecture can be seen to be a function of unconscious thought, in that when we perceive architecture we are not conscious of the mechanisms behind our perception of it.