See Part 1.

The existence of time may seem irrefutable, owing to its pervasive role in our experience. So why do many academics challenge it, or profess to refute it? The answer is twofold, drawing on both metaphysical philosophy and empirical science.

First, let's talk philosophy.

When considering logical, semantic, and otherwise philosophical arguments against the A-theory of time, one has to remember something about many philosophers: they don't base their theories on intuition or the way things seem. Instead, they're willing to abandon their intuitions to defend strange notions based on intangible, logical principles and concrete, almost mathematical rationales.

Thus, the primary strategy B-theorists utilize is that real-time (i.e., the A-theory) contradicts some basic principle of logic or semantics. A famous example of this is Gottfried Leibniz, who held that the notion of objective time violates the Principle of Sufficient Reason: the concept that everything which exists must have a sufficient reason or cause to.

Leibniz asked us to imagine two, nearly identical worlds: worlds with precisely the same laws and events, distinct only in that one is always one second behind the other (when a tree falls in the former, the same tree falls a second later in the latter). He then stated that, with these worlds being identical to one another except for their "times," there could be no reason why one would exist over the other. After all, how could there be any cause for one version of time to obtain instead of the other without any other difference between their respective worlds, any cause for one time to be real and the other not?

There have been numerous responses to this several-century-old argument of Leibniz's. Some question the Principle of Sufficient Reason, others that it proves the B-theory of time. But in response, B-theorists have developed more nuanced arguments, pitting time against other principles of logic and axioms of similar strength -- and in turn, A-theorists have articulated more complex responses, stretching the "temporal debate" all the way to the present.

But this dispute isn't limited to philosophy: it also incorporates aspects of the physical sciences. For instance, Newton held that absolute, objective time exists as an innate force within the universe. Inversely, Einstein famously argued under his theories of relativity that time is an illusion dependent on one's location and speed. To put this into perspective: if I were watching a meteorite plummet towards earth from my driveway, and you were watching the same meteorite while flying 300 miles per second around the moon (just go with it), then we would, according to Einstein, see the meteorite strike earth at different times. Thus, one person's future would be the other's present, making time subjective.

Of course, there are ways to circumvent this problem. Some reinterpret Einstein's theories to accommodate objective time, while others conceive of entirely different theories to explain physical phenomena.

Ergo, philosophically and scientifically, the temporal debate remains unresolved. So, what's your take on it?