Occam's Razor is usually introduced as a preference for simpler explanations.
Given two explanations that account for the same observations, prefer the simpler one.
That's useful as a first approximation, although it can easily turn into a preference for whichever story contains fewer words, fewer parts or less apparent complexity.
Reality has no obligation to be simple.
Sometimes the explanation with seventeen interacting variables is better because there really are seventeen relevant variables. Removing sixteen of them doesn't make the theory elegant. It makes it wrong.
So I've come to think about the razor somewhat differently.
Every claim should earn its keep.
Suppose I observe something and construct an explanation containing three assumptions. Then I add a fourth assumption that doesn't improve what the explanation predicts, distinguish between competing possibilities or account for evidence the first three couldn't handle.
What did the fourth assumption buy me?
Maybe nothing.
Now I have one more thing to explain, defend and carry forward without having increased the usefulness of the model.
That's the kind of complexity I want to cut.
This doesn't mean assumptions are liabilities merely because they're assumptions. Every useful model leaves things out and introduces some structure for relating what remains. The question is whether that structure helps us do something we couldn't do without it.
Sometimes additional complexity earns its place immediately.
A mechanic hears an engine making an unfamiliar noise. "Something is broken" is a wonderfully simple explanation and almost useless for repairing the car. Distinguishing among ignition, fuel, lubrication, timing and mechanical wear makes the explanation considerably more complicated.
The complexity buys diagnostic power.
That's different from adding an elaborate story about why the car chose this particular morning to betray us.
Both stories contain additional structure.
Only one helps us distinguish among possibilities we might actually encounter.
This is where Occam's Razor becomes more interesting to me than a generic celebration of simplicity.
The razor doesn't tell us how complicated the world is.
It disciplines what we're willing to claim about it.
If two models explain the available evidence equally well and one requires several additional commitments that currently do no explanatory work, I have less to lose by carrying the smaller model for now.
The words for now matter.
Tomorrow may provide evidence that requires another distinction.
Then the more complicated model may become the simpler adequate explanation, not because it contains fewer parts, but because removing those parts would now require us to ignore something we've encountered.
That makes simplicity dependent on the question we're asking.
Consider a map.
A road atlas leaves out property boundaries, elevation contours, sewer lines and the location of every tree. That's not because those things aren't real. They aren't necessary for the work that particular map is trying to do.
Give the same map to someone repairing a water main and its simplicity becomes a defect.
They need another representation.
Neither map is the true map.
Each preserves distinctions relevant to a particular purpose.
I think something similar happens when explanations become identities.
A person notices that they repeatedly respond to certain situations in similar ways and eventually finds a description that helps make sense of the pattern.
That description can be useful.
Then more claims accumulate around it.
Because I'm this kind of person, I must prefer these things. People like me behave this way. This experience means that. Someone who challenges the description must not understand me.
The original compression may have clarified something real.
The additions may or may not.
Occam's Razor doesn't tell us to abandon identity or reduce a person to the smallest possible description. A human be