 Valla’s insistence on examining and assessing arguments in terms of persuasion and usefulness leads him to criticize not only the syllogism but also other less formal modes of argumentation. These modes usually involve interrogation, resulting in an unexpected or unwanted conclusion or an aporetic situation. Some scholars have regarded Valla’s interest in these less formal or non-formal arguments as an expression of a skeptical attitude towards the possibility of certainty in knowledge in general. Others have raised serious doubts about this interpretation. What we can say for sure, however, is that Valla was one of the first to study and analyze the heap argument, dilemma, and suchlike. The heap argument is supposed to induce doubts about the possibility of determining precise limits, especially to quantities. If I subtract one grain from a heap, is it still a heap? Of course. What if I subtract two grains? And so forth, until the heap consists of just one grain, which, to be sure, is an unacceptable conclusion. It seems impossible to determine the exact moment when the heap ceases to be a heap, and any attempt to determine this moment seems to involve an ad hoc decision, for a heap does not cease to be a heap due to the subtraction of just one single grain. Valla discusses a number of similar cases, and comments on their fallacious nature.