Philosophy of space and time is the branch of philosophy concerned with the issues surrounding the ontology and epistemology of space and time. While such ideas have been central to philosophy from its inception, the philosophy of space and time was both an inspiration for and a central aspect of early analytic philosophy. The subject focuses on a number of basic issues, including whether time and space exist independently of the mind, whether they exist independently of one another, what accounts for time's apparently unidirectional flow, whether times other than the present moment exist, and questions about the nature of identity (particularly the nature of identity over time).
The earliest recorded philosophy of time was expounded by the ancient Egyptian thinker Ptahhotep (c. 2650–2600 BC) who said:
Follow your desire as long as you live, and do not perform more than is ordered, do not lessen the time of the following desire, for the wasting of time is an abomination to the spirit...
The Vedas, the earliest texts on Indian philosophy and Hindu philosophy, dating back to the late 2nd millennium BC, describe ancient Hindu cosmology, in which the universe goes through repeated cycles of creation, destruction, and rebirth, with each cycle lasting 4,320,000,000 years. Ancient Greek philosophers, including Parmenides and Heraclitus, wrote essays on the nature of time.
Incas regarded space and time as a single concept, named pacha (pacha, pacha).
Plato, in the Timaeus, identified time with the period of motion of the heavenly bodies, and space as that in which things come to be. Aristotle, in Book IV of his Physics, defined time as the number of changes with respect to before and after, and the place of an object as the innermost motionless boundary of that which surrounds it.
In Book 11 of St. Augustine's Confessions, he reflects on the nature of time, asking, "What then is time? If no one asks me, I know: if I wish to explain it to one who asks, I know not.
