Editing Philosophy of space and time (section)

==Realism and anti-realism==
A traditional [[Philosophical realism|realist]] position in [[ontology]] is that time and space have existence apart from the human mind. [[Idealism|Idealists]], by contrast, deny or doubt the existence of objects independent of the mind. Some [[anti-realism|anti-realists]], whose ontological position is that objects outside the mind do exist, nevertheless doubt the independent existence of time and space.

In 1781, [[Immanuel Kant]] published the ''[[Critique of Pure Reason]]'', one of the most influential works in the history of the philosophy of space and time. He describes time as an ''[[A priori and a posteriori|a priori]]'' notion that, together with other ''a priori'' notions such as [[space]], allows us to comprehend [[empirical evidence|sense experience]]. Kant holds that neither space nor time are [[Substance theory|substance]], entities in themselves, or learned by experience; he holds, rather, that both are elements of a systematic framework we use to structure our experience. Spatial [[measurement]]s are used to [[quantity|quantify]] how far apart [[Physical body|object]]s are, and temporal measurements are used to quantitatively compare the interval between (or duration of) [[Spacetime#Basic concepts|event]]s. Although space and time are held to be ''transcendentally ideal'' in this sense—that is, mind-dependent—they are also ''empirically real''—that is, according to Kant's definitions, a priori features of experience, and therefore not simply "subjective," variable, or accidental perceptions in a given consciousness.<ref>See Kant, Critique of Pure Reason, I ["The Elements of Transcendentalism"], Part I ["The Transcendental Aesthetic"], Sections I and II ["Of Space" and "Of Time"])</ref>

Some idealist writers, such as [[J. M. E. McTaggart]] in ''[[The Unreality of Time]]'', have argued that time is an illusion (see also [[#The flow of time|The flow of time]], below).

The writers discussed here are for the most part realists in this regard; for instance, [[Gottfried Leibniz]] held that his [[monadology|monad]]s existed, at least independently of the mind of the observer.