Hi there A_G!
You raise a good and valid point. You don't want to call the findings of science absolute truths. Especially since new information arises and even the example I gave of evolution isn't absolute but always changing as we learn more. Although the data is pretty solid in support for both evolution and psychological hedonism.
But saying it was "actually true", implying that it was an absolute truth, was a bit strong on my part. Thanks for the correction.