Affirmative and positive cause difficulties in their extended use, since each term has negative for its opposite and since both words may qualify identical or similar nouns.
The distinctions are not clearly fixed, but tendencies in usage may be noted. In general affirmative implies denial as its opposite, and positive implies negation, or the absence of truth, reality, or actuality as its opposite. Something that is not affirmative may be destructive; something that is not positive may be null, nonexistent, or nugatory.
Hence, an affirmative philosophy either affirms accepted principles or establishes new ones, and so is opposed to negative philosophies (as skepticism and nihilism).
A positive philosophy (this often equals positivism) deduces its principles from something that is evident to the senses or is from the commonsense point of view regarded as real and factual. Metaphysics is from the positivist's point of view a negative philosophy.
An investigation has an affirmative result when it confirms the hypothesis of the investigator; it has a positive result if something definite is discovered, whether the result proves or disproves the hypothesis.
A person may be said to exercise an affirmative influence when he strengthens or improves something that exists or develops something better to take its place; he may be said to exert a positive influence when he affects others in definite concrete ways.
A defeatist may exert a very positive influence which cannot be described as affirmative; an optimist's attitude is affirmative, but it often fails to exert a positive influence.