Validity can only be supported by facts and even those that can be positively associated with any thought, regardless of its relativity. Actual relativity is the only validity when it comes to facts.

For example.

Imagine a scenario in which a competent representative from every different school of philosophy gathered together to debate on the meaning of life. Obviously, they will all give different answers.

Nihilism within its existential school, points out that there is no objective meaning to life, and because every other school of thought has their own definition to the meaning of life (automatically, making it subjective) nihilism would be the only real truth, because it is the only one that points out a fact that cannot be relative and that is that life has no objective meaning.

Further more, objectivity cannot be defined by a higher power, because not everyone will believe in a higher power (I sure don't). The very concept of a higher power is subject to the person in question, and the lack of scientific proof that a higher power even exists lends the argument (in which a higher power is the objective source of morality) gives it no credibility for any argument, what so ever.