 It is impossible that contradictory attributes such as being and non @-@ being should at the same time belong to one and the same thing ; just as observation teaches us that a thing cannot be hot and cold at the same moment . The third alternative expressed in the words — they either are such or not such — results in cognition of indefinite nature , which is no more a source of true knowledge than doubt is . Thus the means of knowledge , the object of knowledge , the knowing subject , and the act of knowledge become all alike indefinite . How can his followers act on a doctrine , the matter of which is altogether indeterminate ? The result of your efforts is perfect knowledge and is not perfect knowledge . Observation shows that , only when a course of action is known to have a definite result , people set about it without <unk> . Hence a man who <unk> a doctrine of altogether indefinite contents does not deserve to be listened any more than a drunken or a mad man . 
