General realities and truths, world truths, basically, mean the same. In order to use Present Simple in this sense, the general reality must take place in the present. This is important. For general realities and general truths, we can use other tenses too. Past Simple, for example. We can even use Present Perfect or Present Perfect Continuous! So, how do we know that we need to use Present Simple for general realities? The condition is that the reality or truth is always true (generally true). This is the reason why they call it general truths. It was, and most importantly, it is now (that’s why Present Simple) true. It will most probably stay true (at least in the foreseeable future).
As a result, the Moon revolves around the Earth.
Do General realities and truths have to be actually true?
After all, It is not important if the speaker is correct about their statement of general realities. However, it’s important that the speaker believes it’s true, or pretends to believe it.
Two plus two equals five.
We can view general realities, world truths, and general truths as facts. At least they go hand in hand in terms of marginal frequencies (like never and always), and they are, basically, facts… However, I separated Facts in Present Simple into a different category.
See also: Comparison between general realities, unchanging situations, and facts
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