What is the difference between positivism or postmodernism?

Postmodernism is a freedom of choice, as people can choose to be straight or homosexual, to choose what to do with their lives instead of before where a lot of it was governed (such as as patriarchal society). It has also been helped by modern technology; for example, with the introduction of contraception, you can choose whether you want to start a family.

Positivism sounds like Functionalism. Functionalists believes in an overly harmonic view of society, and of a Human Analogy; basically, like the human body, everything must work for it to function. It is critiqued about this however, as Functionalists belives everything is hunky dory (all well) and they love the nuclear family (married couple children), however this is not the case in a lot of places around the world, which are ignored.

Hope I've helped. Maybe search Wikipedia and see if my link to Functionalism seems correct.