Take notice of the language authors willsometime use when they are speculting about things or hoping you won't realize that the evidence is weak: "it is probable or likely that ," (is it probable?) "clearly, this is so " (is it clearly?), "it should be obvious by now" (is it obvious?), "this undoutably means" (is it undoutable?) Remember that forceful words don't necessarily make a weak argument any more convincing.