An argument was a conversation in which individuals gave their opinions in support of or against something. The goal of an argument was to convince an individual of something. Arguments were largely supported by evidence. The relationship between argument and evidence might be counterargued.
In 2265, the USS Enterprise was probing the galaxy's edge when they discovered the disaster recorder of the SS Valiant. After recovering what could be recovered from the memory banks of the recorder, the only sure fact was that the Valiant was destroyed. Captain James T. Kirk saw this as the "best argument" for continuing the probe, because he reasoned that other vessels might come this way and they would need to know what dangers they might encounter. (TOS: "Where No Man Has Gone Before")