Essentialism is an ancient theory about the sources of power and order in the world. Its basic thesis is that the laws of nature are immanent in the things that exist in nature, rather than imposed on them from without. Thus, essentialists hold that things behave as they do, not because they are forced or constrained by God, or even by the laws of nature, but, rather, because of the intrinsic causal powers, capacities and propensities of their basic constituents and how they are arranged. The new essentialism is a modern version of this ancient theory. The new essentialists, like the old, insist that the same things, constituted in the same ways, from the same basic components, would have to behave in the same kinds of ways in any other world in which they might exist, for what they do or could do is of their essence. The things that exist are thus supposed to determine what the laws of nature are, rather than the laws determine how things must behave. But the new essentialism, unlike the old, is a metaphysic for a modern scientific understanding of the world.

The essentialist theory of laws of nature stands in contrast to the “divine command” theory and its modern secular counterparts. According to the divine command theory, the laws of nature are imposed on things by God. They are God's commands for the natural world. Descartes and Newton both thought of laws of nature in this way, and both attributed the existence of invariable laws to the coherence and consistency of God’s commands. According to this traditional view, material things are bound to act according to the laws of nature, because such things are themselves powerless.