Henry Vilas wrote:It's a lot older than Washington. From Ovid, it is also sometimes translated as: "The result justifies the deed."
The meaning seems apparent.
Yes, I am aware of the source. Meaning is rarely just "apparent," however, and rarely stable at that. For example "probare" is much more commonly used to mean "test, examine, evaluate," as in the phrase "the exception proves the rule." Although we now understand that phrase to mean that cases which appear to break the rules actually confirm them, it originally meant, more simply, that cases which appear to break the rules actually test them.
Thinking of "probat" in this more common sense, we can think of "Exitus act probat" as meaning that the ends test or evaluate the means. In other words, the phrase can be read to mean the something different from what we take it to mean today--not that you can do whatever you want in order to achieve a certain end, but that the results are the final evaluation of the means.
Therefore, I prefer to translate it as "It don't mean a thing if it ain't got that swing."