"Arthāpatti" (अर्थापत्ति) means postulation, derivation from circumstances. In contemporary logic, this "pramana" is similar to circumstantial implication. As example, if a person left in a boat on river earlier, and the time is now past the expected time of arrival, then the circumstances support the truth postulate that the person has arrived. Many Indian scholars considered this "pramana" as invalid or at best weak, because the boat may have gotten delayed or diverted. However, in cases such as deriving the time of a future sunrise or sunset, this method was asserted by the proponents to be reliable. Another common example for "arthapatti" in ancient Hindu texts is, that if "Devadatta is fat" and "Devadatta does not eat in day", then the following must be true: "Devadatta eats in the night". This form of postulation and deriving from circumstances is, claim the Indian scholars, a means to discovery, proper insight and knowledge. The Hindu schools that accept this means of knowledge state that this method is a valid means to conditional knowledge and truths about a subject and object in original premises or different premises. The schools that do not accept this method, state that postulation, extrapolation and circumstantial implication is either derivable from other "pramanas" or flawed means to correct knowledge, instead one must rely on direct perception or proper inference.