The Early Buddhist Texts show that during this period many different kinds of philosophers often engaged in public debates ("vivada"). The early texts also mention that there was a set procedure ("patipada") for these debates and that if someone does not abide by it they are unsuitable to be debated. There also seems to have been at least a basic conception of valid and invalid reasoning, including, according to Jayatilleke, fallacies ("hetvabhasah") such as "petitio principii". Various fallacies were further covered under what were called "nigrahasthana" or "reasons for censure" by which one could lose the debate. Other "nigrahasthanas" included "arthantaram" or "shifting the topic", and not giving a coherent reply.