Ken: I don't think it is a matter of if something or someone has always existed, not much debate there; the debate is who or what has always existed. That is where everybody disagrees on.
Ken is exactly right - something, or rather, SOMEONE, had to have pre-existed the universe. But there are two other absolutely necessary attributes of that pre-existing Entity:
This creative / eternal Force behind the universe had to be unfathomably powerful, with the ability to grow what first existed, from an almost infinitely small point to nearly an octillion (that's a 1 followed by 27 zeros) times in size, and in less than a trillionth of a second. And this was no random explosion, but a exceptionally powerful and controlled expansion.
The creative / eternal Force also had to be intelligent beyond what we can conceive, as what it built, designed, and how these things were deployed were astoundingly brilliant and still mysterious, even to our best scientific minds and analysis, for a century now. In just the first THREE MINUTES of the Big Bang's beginning, light elements, such as hydrogen and helium, were formed. When the universe was less than 0.0001 second old, the photons of the cosmic background were so energetic, proton-antiproton pairs were continuously being formed by pair production. However, the proton-antiproton pairs were also continuously being destroyed by annihilation. At an age of just four seconds, the temperature of the universe dropped below 6 billion degrees Kelvin. two minutes after the initial Big Bang, the universe contained nuclei more complicated than a single proton. After three minutes, helium formed by the fusion of deuterium, protons, and neutrons. All of these amazing things of incredible designs were created in just three minutes, and perfectly began to combine, alter and interact in stunning ways. And they had to have a specific sequence in their developments and timings, as the laws of physics observe and that continue to this day. I don't even drink a cup of coffee in three minutes - which makes what physicists say about the universe's beginning so mind-blowing! But as stunningly fast as these things came into existence, in mere minutes, it's not as if this Creative Force were in a hurry, as It wasn't until matter started to dominate the density of the universe (after about 2,500 years) that the universe became transparent (after about 300,000 years) and as stars began forming and started up the process of nucleosynthesis again.
But the existence of EVERYTHING that exists depends upon those first three minutes of the Big Bang. There was a astonishing Mind behind our universe, that also designed and powered it up, and has expanded it beyond comprehension! Blind things can't build and design ANYTHING - it took a purposeful Mind to begin the universe and to set in place it's guiding mechanics and ongoing operation.