Is All Evidence Empirical?

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[Cenderawasih]

On 5/16/2015 at 1:03 PM, motherengine said:

If all evidence must be perceived to be contemplated does this not make all forms of evidence technically empirical?  Even 'pure' logic has a root basis in perception.

I haven't read through the entire thread, so forgive me if I'm repeating what others may have said . . .

First of all, given the nature of the site, I'll just stick to scientific evidence.

My answer to the thread title would be, like so many things related to science, it depends who you ask.

A strict empiricist (Bas van Fraassen, say) would tell you "Yes! All evidence is empirical. The only factor that counts toward the epistemic warrant for a scientific claim is its fit with the facts".

Of course, though, not everyone is a strict empiricist. Those of a more realist persuasion (e.g. the later Einstein) are likely to tell you that, in addition to its fit with the facts, other factors such as simplicity and explanatory goodness also constitute evidence to support a theory or hypothesis.

To be more clear, suppose we have two rival theories, T1 and T2, which are empirically equivalent, i.e. they both entail precisely the same set of empirical consequences; they are empirically indistinguishable (as is the case, for example, with all the various interpretations of quantum mechanics).

Suppose further that T1 is simpler than T2, or that T1 provides a better explanation of the facts than T2 (however these things are defined).

The strict empiricist would likely tell you that we should choose T1 over T2 . . . as a matter of pure pragmatics. A simpler theory, after all, is easier to work with than a less simple rival.

The realist, on the other hand, would agree that we should prefer T1 over T2, but not merely on pragmatic grounds. T1's greater simplicity or superior explanatory virtues provide a reason to believe that T1 is more likely to be true than T2.

In other words, to the realist, but not the antirealist (e.g. the strict empiricist), simplicity and explanatory power count as non-empirical evidence for that theory.

Einstein, to cite a notable example, falls into the latter (realist) camp. His writings are laced with remarks that non-empirical virtues such as the beauty, elegance, simplicity, etc. of a theory constitute evidence for that theory.

[Cenderawasih]

Reading through the (quoted) OP question again, I was wondering if my remarks above may have been slightly orthogonal to the question posed. So, if I may add a little more . . .

The OP question again was: "If all evidence must be perceived to be contemplated does this not make all forms of evidence technically empirical?"

Is posing the question in such a way not tantamount to trivializing the concept of evidence? To turn it into a vacuous tautology? All evidence becomes empirical evidence by sleight of definitional hand.

If empirical is understood to mean "perceived through the senses" then the question reduces to a vacuous "If all evidence is empirical is it not the case that all evidence is empirical?"

And the answer is an obvious "Yes!" -- by virtue of a Pickwickian (i.e. non-standard) and circular definition.

But who says evidence has to be perceived through the senses?

The beauty, elegance, simplicity, explanatory goodness, etc. of a theory are not what we would normally regard as being directly perceived. There are those, however, namely scientific realists, who hold that such non-empirical virtues of a theory nonetheless add to the epistemic warrant for that theory. In other words, said virtues constitute non-empirical evidence for that theory.

It could be I'm misunderstanding something. Any input from other members is welcome.
 

[Cenderawasih]

Continuing from above, consider the following extract from Michael Strevens' "The Knowledge Machine" . . .

 

" "It is more important to have beauty in one's equations than to have them fit experiments," wrote the English theoretical physicist Paul Dirac--the beauty being a sign that the theory was on the right track and that the discrepancy with experiment was likely "due to minor features . . . that will get cleared up with further developments." Beauty is the beacon; truth is what it marks. Einstein, according to the physicist Eugene Wigner, thought along the same lines: "The only physical theories which we are willing to accept are the beautiful ones." You needn't look far to find similar sentiments behind many doors in the corridors of theoretical physics or in the popular writing of physicists such as Subrahmanyan Chandrasekhar, David Deutsch, and Frank Wilczek."

(Michael Strevens, "The Knowledge Machine", p227. Dirac quote from "Evolution of the Physicist's Picture of Nature", p47)

Then . . .

"On a number of occasions, [Murray] Gell-Mann declared his allegiance to the Platonic precept that truth and beauty are entangled, saying in an informal talk, for example, that beauty, simplicity, and elegance are "a chief criterion for the selection of the correct hypothesis."

(ibid, p234)

 

 

Now, if the beauty, simplicity, elegance, etc. of a scientific theory/hypothesis are non-empirical virtues (as they appear to be), and that we understand evidence intuitively as "a reason to believe something is true", then we must conclude that not all evidence is empirical.

 

Beauty, simplicity, elegance, etc., are considered to be non-empirical evidence by the abovementioned scientists.