Immanuel Kant's epistemological philosophical system which holds that space and time are not properties of independent real things in themselves, but are rather a priori intuitions possessed by our minds, and
everything we perceive is subject to this space and time intuition. However, as opposed to George Berkeley's subjective idealism which holds that
nothing exists
outside the
mind, Kant's transcendental idealism accepts the existence of external objects independent of our mind but distinguishes between noumena (things-in-themselves as they actually are) and phenomena (things as we perceive them), we can only Intuit the phenomena (or the appearance of the object) from the noumena (which we can
never directly perceive). Thus Kant acknowledges that while we can never know the noumena, the phenomena sufficiently conform to our concepts of them and that in order to make sense of the empirical
world, we must presuppose transcendentally a consciousness that unites intuitions under concepts.
