I am referring to things like Plato's Republic or The Art of War. Any historical text for which the full original text cannot be found. Although full versions of these texts are available today and attributed to these authors, isn't there great uncertainty about whether the contents are correct? Do you just keep in the back of your mind that everything was actually from a copy by someone later in history, so there are likely a lot of inaccuracies?

Also when I want to talk about of these historical texts, should I use words like allegedly, supposedly, etc. because it's not certain the texts were by these people? Or are the modern copies generally accepted to be faithful reproductions of the old texts, so I should just use them as if they were factual? For example if I want to talk about a strategy in The Art of War, can I just say that since it's in the Art of War, the strategy must have been around in the 5th century BCE when the text was supposedly written?

I feel like everything is so uncertain, so I'm not sure with how much certainty I should talk about these things.