Evidence and Truth

Skeptics will often say something like this: “A claim must be supported by evidence.”

The sentence might sound simple (and perhaps obvious), but it is more complex than it seems. It involves a fair assessment of the claim, judicious demands for evidence, and objective interpretation of the evidence. How one judges a claim is just as important as the claim itself.

Now some of the counterarguments go something like this: “How can anyone be an objective judge? Isn’t everyone biased?” Some, who have thought about it long enough, continue like this: “How can we know anything is true?”

That is an example of postmodernist thought. Ignore the large word for now (the Wikipedia entry is confusing and useless), and just realize that many people have come to question the world this way. Anytime a claim is presented, with supporting evidence, they can retort: “How can we know anything is true?”

Following this logic takes us nowhere. You can ask this question so many times that you begin to question the true existence of the trees outside. How do you know they are truly there? Because you can see it? You can see trees in movies, too. Doesn’t mean they’re in front of your face. Because you can touch it? Smell it? How do you know that your senses are not fooling you? How do you know you’re not dreaming the texture of bark against your fingers, and the smell of the Earth beneath your feet?

Remember, a skeptic would say this: “A claim must be supported by evidence.” In our example, the claim is that a certain tree outside exists. Now we get to the second part, a judicious demand for evidence. The postmodernist would be completely confused at this part–he does not demand evidence, he only questions the veracity of things. In effect, he is a judge who arbitrarily dismisses claims without regard for the evidence. This is why his logic goes against the foundations of skepticism.

A skeptic would agree that your senses provide evidence that the tree exists. We can also test the claim in other ways: if other people’s senses agree with you, then you have more supporting data. You can assume the existence of other objects and see if the tree interacts with these objects: can you climb the tree? Can you chop off a branch with an ax? Then it probably exists. The postmodernist who argues that nothing exists might say that the test is invalid, and that we cannot assume other things exist. I would reply, “So you don’t exist either. Life is meaningless and purposeless because life does not exist. Please go ponder that while I get on with my life.”

Some of the questions he asked were not entirely absurd. I think that questioning things–perhaps everything–is essential to being a skeptic. But skeptics also guard against the postmodernist trap of illogic, where nothing can be proven. That’s no way to test claims, much less lead a life that assumes attainable truth. Imagine if scientific experiments were run that way:

Galileo: The orbits I have observed don’t seem to indicate that everything orbits the Earth. It must orbit the Sun. Then again, how do I know I’m here? How do I know that the orbits are really orbits and not aliens moving around in the sky? How do I know there is a sky? How do I know that I am thinking?

Galileo’s assistant: Um, sir, the Church is waiting for your reply to their condemnation of heresy.

Galileo: How do I know that the Church exists? Tell them I don’t care. Maybe geocentrism is right! Maybe my simple explanation for all the extra loops in the orbits is wrong. I’m biased, I admit it.

Galileo’s assistant: I guess…I’ll tell the Pope that geocentrism is okay.

Skepticism, however, does not have lax standards of evidence. It is demanding, but not so absurd that proving reality or truth is impossible. More on this topic later.

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Vy is a recent graduate working in a neuroscience lab with children and monkeys. She likes sewing, knitting, lifting weights, and reading in her free time. Especially reading about science!

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