William Lane Craig briefly explains that the begining of the universe cannot be denied or refuted. Some have suggested that different scientific models (like steady state model, oscillating models, quantum vacuum fluctuation models, inlationary models, chaotic inflationary models, ekpyrotic cyclical models, etc.) suggest the universe is eternal from the past. But Craig explains that modern physics has shown the universe began at the point of the Big Bang due to the Borde Guth Vilenkin Theorem