Truth

Truth is factually what is happening, happened, or will happen.

Science
In science, truth is what happened independent of observers. What happened contains every atom of the universe, in every moment. Atoms change location from one moment to another, and in this context fact is an uninterrupted film clip of the Universal Movie.

This must be contrasted with assumptions, which are selections of the Universal Movie that our brains intentionally or unintentionally splice together into one conceptual film. When a testamony is given of these assumptions, it is called a Statement of the Facts.

Everything true must exist. To have the adverb "exist" apply to it, something must have a physical presence within space. For something to exist it must have a potential to cause  or be amenable to displacement; be amenable to gravitation; it must have the ability to cause or be amenable to displacement. Existence is therefore a property of the subset of nouns  subject to gravitational  and electromagnetic  forces.

That which does not exist is abstract.

Political Considerations
Whoever can persuade the majority of people that their view is right on a mass scale controls public opinion. The mainstream point of view is currently centralised by cathedral social verifiers. Cathedral social verifiers attempt to reproduce objectivity, rendering matters of opinion the realm of individual speculation. The effect on a large scale is memetic extinction. Thus, the majority of people are likely to agree on most issues. Such a presentation of points of view is an important part of maintaining control in a democratic regime.

What becomes a matter of opinion is a subject which the social verifier views as challenging to its worldview. For the cathedral, this includes topics such as whether hierarchies are good or bad, whether human biodiversity exists or not, whether to vote in elections or not. Strictly speaking, what the cathedral or any other factional approach to social verification considers opinion, is a matter on which one can make a true or false statement. Each faction decides what questions to make arguments to truth on based upon their own interests. For Resartus, this means anticathedral ideas, hence it is the antiversity.