The thermal limits of natural selection.

[NichG]

Belief does have a formal usage in statistics via the Bayesian formalism, and in turn can mean something specific in a scientific context when it comes to things like hypothesis testing and the interpretation of particular evidence.

But that still means that the thing it's attached to had to be a sufficiently precise claim such that it makes quantitative predictions of the relative probabilities of different possible experimental results compared to some other hypothesis.

So e.g. I have no problem with the phrase 'I believe in the second law of thermodynamics because of this collection of evidence'. It's just weird to say 'I believe in entropy' in that same sense. I'd say the same with natural selection. Natural selection itself isn't a hypothesis, it's a term defining a process. A hypothesis would be something like 'natural selection is responsible for the physical features of all life on Earth' or 'natural selection is inevitable in any system containing replicators'