I think if we take Al Mortiz’s distinction between scientific evidence and philosophical conclusions inferred from that evidence (as we should), we cannot say that the scientific evidence we have indicates that the universe came into being.
This is because things can only come into being if a certain philosophical theory of time is true, and our scientific evidence itself does not favor any particular philosophical theory of time. Thus, the only thing the scientific evidences such as the expansion of the universe, or the CMBR, or the Borde-Guth-Vilenkin theorem (etc.) indicates is that the universe had a first or initial state. Whether or not this state came into being is a conclusion we can only draw once we endorse a particular theory of time and conjoin it with the scientific evidence.
These competing theories of time are broadly known as the A-theory and the B-theory.
The former basically says that there is a real temporal transition from event to event, and from state to state. Time seems to ‘flow’ like a river on A-theory, the ‘present’ is an absolute reference frame from which we can say what is ‘really’ the past, and it’s generally said once something passes from present to past it ceases to exist.
B-theory, on the other hand, says that time-space is like a giant ‘block’ that’s divided into slices. Each of these slices exists, none being less real than another. Time is like a spatial dimension. What we call the ‘present’ is the time-slice we’re at, but other things are at different time-slices and thus the ‘present’ is in their region of the block to them. There is no absolute ‘present’ or ‘past’ or ‘future’, no absolute reference frame from which we can say what is ‘really’ the past, since all time-slices equally exist.‘Future’ and ‘past’ are like directions in the ‘block’. e.g., Dinosaurs exist in a time slice earlier than this one. (Time-travel is only possible on B-theory, since only on B-theory is there ‘somewhere’ to travel to in the past)
Things can only ‘come into being’ if the A-theory is true. But, many, many scientists and philosophers are B-theorists (most were because of Einstein’s theories of relativity) and they’re perfectly capable of accepting Big Bang Cosmology etc. So, Big Bang Cosmology by itself cannot tell us whether the universe came into being, it’s left up to us to discover the best philosophical interpretation of the scientific evidence.
As one of the world’s foremost experts on the Kalam cosmological argument (which specializes in the scientific and philosophical evidence for the temporal beginning of the universe), Dr. William Lane Craig, explains:
“On a B-Theory of time, the universe does not in fact come into being or become actual at the Big Bang; it just exists tenselessly as a four-dimensional space-time block that is finitely extended in the earlier than direction. If time is tenseless, then the universe never really comes into being, and, therefore, the quest for a cause of its coming into being is misconceived. Although G. W. F. Leibniz’s question, Why is there (tenselessly) something rather than nothing?, should still rightly be asked, there would be no reason to look for a cause of the universe’s beginning to exist, since on tenseless theories of time the universe did not begin to exist in virtue of its having a first event anymore than a meter stick begins to exist in virtue of having a first centimeter.” - Craig, William Lane., and James Porter Moreland. The Blackwell Companion to Natural Theology. Chichester, U.K.: Wiley-Blackwell, 2009. pp. 183-84.
