Prudence, indeed, will dictate that governments long established should not be changed for light and transient causes . . in the passage above, which word provides a context clue to the meaning of transient?

The answer is: light.

The statement above, of complicated and deep political implications, states that forms of government, if they should change, they should follow complex historical and economic processes, and not the fancy of some based on a passing whim. The only word that could give context to the explanation above, and therefore, to the word transient, is “light”, that is to say, fleeting.

answer; /// (the anagnorisis )