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How do I get rid of the ungrounded assumption that evidence exists?

by Bob Jacobs1 min read15th Oct 202014 comments


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There is an underlying philosophical assumption in my worldview that I can't get rid of. It states:

"Evidence exists"

Math, science and philosophy are all build upon this assumption. Everything in my worldview I can either support or eliminate with evidence, except for this assumption. Because if I try to give reasons for this assumption I'm already assuming that those count as evidence for the thing I'm trying to proof: I'm begging the question!

Does anyone know how I can get rid of this ungrounded assumption?

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I don't think you can, at least not if you want to have a worldview in the first place. Any system of reasoning needs to have some axioms.

See also Where Recursive Justification Hits Bottom for an argument for why this isn't a problem.

If you start with the model of an embedded agent in a partially internally predictable world (it has to be at least partially internally predictable, otherwise embedded agency would not make sense), the rest falls out of that. If you define an embedded agent as a subsystem that has a course model of the world and a set of goals to optimize the world for, as well as a way to interact with the outside world, then "evidence" is just that interaction with the outside world, processed and incorporated into the map, and sometimes into the goals. So, the assumption "evidence exists" is grounded in the idea of embedded agency. 

If, on the other hand, you reject that approach in favor of another one, it pays to explicate your model of the world first. Is it solipsism? Cartesian dualism? Something else?

It's another unfounded assumption that you should disbelieve in anything you cannot prove all the way down.

I don't think you need the concept of evidence. In Bayesian probability, the concept of evidence is equivalent to the concept of truth; both in the sense that P(X|X) = 1, whatever you consider evidence is true, but also P(X) = 1 --> P(A /\ X) = P(A|X), you can consider true sentences as evidence without changing anything else.

Add to this that good rationalist practice is to never assume that anything is P(A) = 1, so that nothing is actually true or actually an evidence. You can do epistemology exclusively in the hypotethical: what happens if I consider this true? And then derive consequences.