Ockham’s Razor is the heuristic sometimes known as the lex parsimoniae: the Law of Parsimony. As he actually proposed it:
Numquam ponenda est pluralitas sine necessitate: Do not posit pluralities beyond necessity.
Ockham’s Razor as it is usually rendered:
Entia non sunt multiplicanda praeter necessitatem: Do not multiply entities beyond necessity.
The entities of a theory are its terms. They are not actual entities, but formal only. So the Razor is often rendered:
Do not multiply terms beyond necessity.
This makes it easy to compare theories and see which one is more parsimonious – especially if they are mathematically formalized. F = ma, for example, clearly invokes three terms, that terminate on three sorts of properties of things. The basic idea of course is that as between two theories that adequately explain some phenomenon, the simpler is more likely to be more accurate. But why?
In Finality Revived: Powers & Intentionality (Synthese, March 2016), David Oderberg suggests in passing that Ockham should instead have proposed:
Do not multiply mysteries beyond necessity.
There are two ways to multiply mysteries: to increase terms beyond adequacy, or to decrease them beneath adequacy. Oderberg’s version of the Razor covers both.
If you decrease terms too much, your explanation is inadequate. One common result is that you end up failing to explain all sorts of related things. For example, the modern rejection of final and formal causation can’t account for mind, freedom, complexity, or order; whereas under the Aristotelico-Thomistic Grand Synthesis that modernism had displaced, they had posed no particular problems.
If your explanation produces mysteries that your former explanation understood, then you are on the wrong track.
If on the other hand you increase terms too much, you introduce new mysteries; for, when it is first noticed, every new mystery is denoted by a new term; and vice versa. So, to introduce a term just is to introduce a new mystery, or rather to notice it. Every new term notices and relevates a new explanandum, each of which calls out for a new explanans, and bedevils us until we get it. This is a formalization of the fact that each new thing we learn increases the surface area of our ignorance; increases the precision of our understanding of how much we have still to learn.
Viz.: F = ma raises the question: what are Force, mass, and acceleration? These are defined in terms of other entities, and each such term must itself be explicated in terms of yet others. That’s not always difficult to do, but it must be done, if the explanation is to amount to more than hand waving.
So: don’t add a new mystery by adding a new term if in so doing you are not clearing up at least one old mystery.
God is the only term that does not introduce another explanandum – although he does of course introduce another mystery. For, while he needn’t be explained, nor can he be explained. Nevertheless no explanation that does not ultimately terminate and rest upon him can be complete, or therefore satisfactory; for it cannot otherwise rest, or therefore explain. Notions alienate from the Absolute cannot ultimately work; they break down; they fail; they stultify; they negate; they kill.
In the perfect and complete explanation, only one mystery remains: God.