Irreducible complexity is a notion introduced by Creationists in an attempt to undercut the theory of evolution by natural selection, essentially by proposing that some features found in nature are so complex even at their most fundamental levels that they could not have been arrived at through evolution.

This is a debunkable notion, especially given recent molecular evidence pointing to a Universal Common Ancestor. But interestingly, because of the Creationist focus on nonevolved life, the idea has not been much applied to nonbiological fields. And yet, there is one field to which this idea truly does belong, and that is particle physics. Within particle physics an equation has been developed, a very long and complex and powerful equation describing the intricate balance of relationships between all of the particles and forces of our Universe which combine to give it its perceivable physical characteristics. This is the Standard Model of Particle Physics (and here, to be especially exact, the Standard Model Lagrangian -- a Lagrangian being an especial sort of comprehensive description of a system).

Now, here's the thing, the equation is an equation of the whole; it is complete, and inseparably so. No part of the equation may be taken out without the function of the whole collapsing -- and that function is the sustainment of our Universe itself!! Every constant needed to insure our existence is there, and not only to insure that our Universe exists and continues to exist, but that it grows instead of collapsing on itself. And, even more, that this growth is steadily paced and will happen to yield expressions of fundamental forces such as the strong nuclear force and electromagnetism, which happen to contribute to the progressive diversity of chemical elements.

One of the fundamental questions of science and philosophy is, why is there something, instead of nothing at all? Well, now we know that the mechanisms set forth in the Standard Model require there to be something, force 'something' to come seemingly from nothing. But the Standard Model is a something which necessarily precedes every other something which otherwise comes from nothing. And therein lies the rub, for this complex and massive balance of equations is asserted to exist of its own accord, despite the centuries man has had to progress, and the decades mathematicians have had to labor, in bringing to light the glory of its elegant complexity. And this, the atheist contends, is a raw fact, a Universe from nothing.