The above postulation that Mankind is the measure of all things is incorrect on several accounts, meaning that mankind is not the measure of all things. That mankind is not the measure of all things is underscored by the fact that man in all his advancement, has not grasped mentally, or intellectually, all things. Things that remain outside man's comprehension are thus unknown, unnamed and as such, cannot put in human terms. In an abstract sense for instance, this may be underscored linguistically by the inconsistency that exists between the signified (the actual form) and the signifier (the word). There are certain names (means of man's measurement and also the signifier) which denote elements which do not in exist rationally, such as hobgoblins or goblins.
Postulating further that all things that men are they are is also wrong, because, man by himself has not come to understand the essence of man. Concepts that pertain to human nature, crime, benevolence still remain beyond sociologists', philosophers' psychologists' and anthropologists' grasp. That no scholar has ever given a totally satisfying answer on for instance, Hitler's attempt to annihilate the Jews through the Holocaust underscores the veracity of the standpoint that mankind is the measure of all things. It would be inaccurate to render that which cannot measure itself as the measure of all things.
Contrary to the postulation that mankind is the measure of all things; objectivity and empiricism are the constructs that should be deemed worthy of being accorded such dicta and statuses. Without objectivity, man is left with no recourse to feelings and personal experiences which are too fickle and subjective to be put to analysis. (Scientific) knowledge cannot be considered cogent or solid if premised on subjective human experiences. For instance, by merely feeling healthy and strong, it would be inaccurate of an individual to surmise that he is HIV negative even after having protracted sessions of endless flings of illicit and unprotected sex. It is until the person undergoes through empirically-set provisions and constructions (ie. the HIV-AIDS test) that the person is able to know his status.
Similarly, the measure of all things is known to be independent of man. This standpoint is validated by the fact that there are certain constructs or elements that have meaning on their own accord but have not yet been discovered by man. Even before the discovery of certain life forms, the very life forms existed, just as Saturn existed as sixth planet, even before man discovered it. The fact that things exist on their own accord prior to being found or discovered by man only means that man is not the measure of all things.
Critically considering that man is bound by space and time further confirms the inaccuracy of the argument that man being all things, what he is not, the rest are not. That metaphysical elements exist is a matter that renders man as not being in charge (of all things). Russell's Logical Atomism that metaphysical entities are figments of imagination that can be replaced by logical constructions have never been seen to answer certain phenomena such as Demon Possession, Astral Projections, (Black and White) Magic, Sorcery, Witchcraft, among others. The fact that man has not given an element a meaning does not mean that the element has no meaning. On the contrary, the failure to give things meaning only underscores man's limitation (even in terms of space, time and intellect). To quip that death has no meaning just because man's scientific rationality has never grasped the full essence of death and how to thwart it would be definitely a grave blunder and a way too easy out of problems