Time has acted for humans as a 'cement' for causality.
We understand causality as A>B>C etc. The concept of time allows us to grasp the concept of causality (or the other way round, I'm no baby neuroscientist).
If we are at 'B' we know that its 'cause' was 'A', a unique causative action in time that is both unique, and strictly remains in what we term the past. In most cases (though not all), it would seem very strange for us to perceive 'B>A', just as it would seem strange for us to find 'C>B'.
It is this causative normativity that grounds our perception and understanding of the world around us, and underpins science, as much as any other subject.
All this, however does not mean that our causative understanding of the 'flow of time' is in any way real. It may just be an illusion that we maintain cognitively to make sense of the world.
One might be on firmer ground if one maintained that 'causality exists', rather than 'time exists', but to my mind both are very closely linked.
It is of interest that MacTaggart, as an idealist was continuing in the millennial battle between the Eleatics (particularly in his use of Zeno's philosophical method), and the Heraclitians over whether all is
stasis, no change, no time; or whether all is eternal flux, ever flowing, ever-changing.
Just as Zeno sought to prove that motion and time could not exist (to further his wider philosophy), McTaggart sought to prove the irreality of time (to further his).
I still feel that Zeno deserves some special award for posing a set of paradoxes that took 2000 years to solve (and even then not to the satisfaction of all philosophers)
