There is no point in time when the “stuff” that comprises the universe did not exist. Why must it have a cause? Or, why must a finite being be caused by something else in order to exist?
This is a good point. When (if I may so use that term) there was no universe, there was no time either, so there is no instant at which it was caused. Saint Augustine explained it as follows:
“Beyond all doubt the world was not made in time, but with time” (Saint Augustine, City of God, 11:6)
Nonetheless, it is still reasonable to say that the universe was caused, as Catholic physicist Stephen Barr argued in his book
Modern Physics and Ancient Faith:
“ I]f one thinks about it for a while, one can see that a thing can be caused without necessarily having had any beginning in time. For example, imagine that an object is illuminated by a lamp. The lamp is the cause or explanation of the object’s being illuminated. However, nothing in that fact tells us whether the lamp has been illuminating the object for a finite time or for infinite time. If the lamp has always been illuminating the object, then the illumination of the object had no beginning, but nevertheless it always had a cause” (Modern Physics and Ancient Faith, page 33)
Even the big bang model doesn’t really have a beginning of time. Consider, at “t=0” there is no universe, so there really is no time either; in other words t is undefined. At t=.0001 seconds, for example, the universe already existed at a previous time, so it wasn’t caused at that time. Going back further, at t =.000001s, the universe already existed then too, so it wasn’t caused then either. Since time is a continuum, which is divisible
ad infinitum (cf. Aristotle, Physics, Book III), we may continuously find earlier instants in time at which the universe existed, none of which will ever be the first moment. Thus there was no first instant of the universe. Nonetheless, we may say that it approaches t=0 just as a function in calculus approaches, though never reaches, its limit. Thus we may say at the limit of its existence, the universe had a beginning. Regardless, it is reasonable to assert that it is caused because even eternally static things have causes (as Barr argues).
Hope this helps/ makes sense,
-Ryan Vilbig
ryan.vilbig@gmail.com