The ancient Greek philosopher Protagoras is famous for his saying that man is the measure of all things. Though we don't know much about Protagoras or his written work except for quotations appearing in other ancient works, the general view is that Protagoras was the father of moral relativism in philosophy.
Protagoras's complete statement has been translated as follows: "Of all things the measure is man, of the things that are, that [or "how"] they are, and of things that are not, that [or "how"] they are not." It is unlikely that Protagoras believed that physical truths about the natural world such as the freezing point of water depended on one's personal standpoint.
But under Protagoras's tutelage in matters of values, we are left only with the measuring instrument called "man" (or more inclusively "humans"). In the age of the Anthropocene—that still-not-official geologic age in which humans are designated as the most potent geologic force on the planet—those issues thought to relate solely to the lives of humans do NOT, it turns out, relate simply to humans.