Origen's On First Principles is a rigorous text, written by Alexandrian scholar and early Church Father, Origen, around 185 CE. His vast tract on the nature of Christianity addresses subjects such as the Trinity, free will, the end of the world, and Scripture. The treatise On First Principles is in some sense doctrinally aloof (and some scholars suspect that Origen was labelled a heretic when On First Principles was released to the public). This is likely to be true, as Christian North Africa, in addition to being a center of scholarship, was a hotbed for opposing doctrines and a wellspring of heterodox Christianities.

The major themes of On First Principles, especially those which mark it as unique, include his analogy of God to the sun; we can't see it materially by looking at it, but we know it to exist by how it illuminates all else.

Origen's eschatological discussion proposes that "after the end of this present world, others will take their beginning," (Book IV, Chapter 5). Our current world is thus not the only one, but several worlds do not coexist at the hands of God.

Origen also endows humans with free will, and claims that, at the time of creation, God "conveyed invisibly a share in Himself to all His rational creatures, so that each one obtained a part of Him exactly proportioned to the amount of affection with which he regarded Him." (Book II, Chapter 6). Origen accounts for the varied circumstances into which individuals are born by declaring that human souls move toward or away from God before being incarnate in human bodies. That is to say, the positions in which individuals find themselves are a product of their behaviors, as these behaviors are representations of their rational and free will with which all individuals are endowed.