Parsimony and Belief Burdens
Parsimony is not a dislike of complexity; it is a demand that added assumptions earn their keep.
What Parsimony Does
Parsimony asks us not to multiply assumptions beyond need. It does not say the simplest story is always true. Reality can be complex. The point is that complexity should be purchased with explanatory gain.
When two explanations account for the same evidence, the one with fewer unsupported commitments usually deserves higher prior confidence. Added entities, powers, intentions, exceptions, or hidden mechanisms create belief burdens.
Assumption Stacks
Many beliefs become fragile because they depend on a stack of assumptions. Each assumption may be possible, but the conjunction becomes less likely unless the evidence strongly supports the whole structure.
Credencing makes this visible by asking what each assumption contributes and how strongly it is supported. A claim that requires ten weak supports should not inherit the confidence of its most attractive part.
Parsimony and Priors
Parsimony is closely related to priors. Before considering a specific piece of evidence, some hypotheses are less expected because they require more special conditions. That does not make them impossible. It means they need stronger evidence to become competitive.
This is why extraordinary claims require not only evidence, but evidence strong enough to overcome low prior probability and live alternatives.
When Complexity Is Worth It
Complexity is justified when it explains more, predicts better, unifies independent evidence, or survives tests that simpler alternatives fail. The history of science includes many complex theories that earned their place by performance.
The problem is not complexity itself. The problem is unpaid complexity: assumptions added mainly to rescue a preferred belief from evidential pressure.
A Belief-Burden Audit
To audit a belief, list the assumptions it needs. Which are independently supported? Which are introduced only because the conclusion needs them? Which could be removed without losing predictive power?
Then assign confidence to the whole structure, not merely to the most emotionally appealing assumption. Parsimony keeps credence from being inflated by hidden costs.
The Backpack of Assumptions
Every extra assumption is like another object placed in a backpack before a long hike. One item may be harmless; twenty may change the whole journey. The question is not whether each item is possible, but whether each earns its weight.
Parsimony asks a belief to carry only the assumptions it can pay for with explanatory gain, predictive power, or independent support.