I was motivated to start this thread by reading rogersherrer's post on the Cosmological argument.

First, the ultimate cause of anything, our Big Bang Universe included, needs be nothing more than something of the order of a quantum scale random 'twitch'.

'Infinite regress' only requires some special 'cause-less' entity to initiate it on the assumption that a cause be necessariiy greater in at least some respect than its effect. Which is a total, medieval misconception. We observe progressive, spontaneous growth of order, complexity, and consciousness every day, subject only to the availability of an energy source. An infinite regress of temporal events of diminishing scale does not require an infinity of time or space, since the mathematical sum of an infinite converging geometric series is finite, such as 1 + 1/2 + 1/4 + 1/8 + 1/16 + ... to infinite terms = 2. So it most definitely CAN exist. In reality, that would stop at around the Planck scale.

It is only the assumption of an infinite sequence of ever greater causes that leads to a problem, which requires the positing of a 'causeless' initiator.

In the current understanding of science and math, that is not necessary.

A purported state of existence preceding the Big Bang could be a 'sea' or 'field' of energy at the lowest possible state allowed by Quantum Theory, which, being in the maximum state of disorder, or entropy, could persist indefinitely without any violation of thermodynamic laws.

Within the context of any Big Bang universe, initiated perhaps by some random quantum scale twitch, it will eventually expand to an extent where everything drifts apart. Meanwhile, each such universe will have gone through an period where conditions were maximally appropriate for life.

An oscillating universe, where the expansion eventually slows down to start collapsing, and then rebounds in a new Big Bang, is indeed no longer regarded as likely, particularly as the evidence seems to point to our universe accelerating in its rate of expansion.

It has been proposed that some of the fragments of that vast expansion, perhaps under the increasing influence of 'dark energy' which seems to be driving the increasing expansion, could seed new Big Bang singularities, leading to an indefinite and expanding sequence of such universes.

A side note on violations of matter/energy conservation that are often raised as problems with the Big Bang scenario, although I didn't notice it this thread. The consensus is that when the mathematical 'negativity' of gravitational potential energy, as against the energy of matter and the other forces, is computed for, the net energy/matter in our Universe is zero.

Even if some 'first cause' is necessary, it need be nothing more than a random energy fluctuation. Nothing like a God is remotely necessary, certainly no consciousness required.

The KCA is based on several obsolete ideas.

A God cannot explain its own existence, so it solves nothing, especially now we know that most of the puzzles and assumptions it was invented to 'solve' arise from ancient misconceptions.