I had to look that one up. One definition I found was:
the form of empiricism that bases all knowledge on perceptual experience (not on intuition or revelation)No wonder the philosophers dumped it! It was about to put them out of business!
Unfortunately, positivism means different things in different areas of expertise. Logical positivism was killed off by Goedel, but historical positivism lives. Positive in this sense is not the opposite of negative but the other, similar-sounding term spelled the same meaning that which is placed or posited. Completely different word even though spelled and pronounced the same, like half our wonderful language.