So you might have noticed a scroll saying: 誠者天之道也人之道非

Before I explain what this means, I need to explain the original proverb in Classical Chinese it’s ostensibly based off of. The original says 誠者 天之道也 誠之者 人之道也

This translates to “Truth is the way of the Heaven, truthfullness is the way of man.” The quote is part of a larger comment of human virtue. The rest of the quote explains that while the universe’s laws or the way of the world simply are, man must choose to be truthful and perservere on that path. It plays into two slightly different meanings of 誠. One is “truth” as an absolute property of the universe and might better be described as “reality”. The other is “truthfullness” or sincerity as a property of a person.

The scroll however, reads as “Truth is the way of the Heaven, not of man.” Whether this is meant to be a paraphrasing of the original quote with the same intended meaning, or a variation with a different meaning is somewhat unclear. If it was intended to mean something different, it could be interpreted as meaning that man has no influence over the absolute reality of the universe.
We chose to translate this as “Sincerity is the way of Heaven. The attainment of sincerity is the way of men.” because it was more poetic and kept to the meaning of the original proverb.

The full kanbun:
誠者，天之道也；誠之者，人之道也。誠者不勉而中，不思而得，從容中道，聖人也。誠之者，擇善而固執之者也。
Sincerity is the way of Heaven. The attainment of sincerity is the way of men. He who possesses sincerity is he who, without an effort, hits what is right, and apprehends, without the exercise of thought;– he is the sage who naturally and easily embodies the right way. He who attains to sincerity is he who chooses what is good, and firmly holds it fast.

Hope you learned something about Chinese philosophy from your borderline hentai animu ;D