In all intellectual activity, I adhere to the three laws of thought formulated by Aristotle and his followers. These laws of thought do not tell us the limits of what exists, but only the limits of what can be coherently expressed in language.
The first law of thought is the law of identity. Under this law, a thing is itself. “A” is “A.” “Life is life.” This is a law of consistency in meaning across time within a given discourse. A concept must be used consistently within a discourse in order for the discourse to have any kind of internal coherence. Whether a discourse corresponds to experienced reality is a separate question, but a discourse that is not consistent with itself cannot be understood by the human mind as it is presently constituted.
The second law of thought is the law of noncontradiction. Under this law, a thing cannot be both itself and its opposite. “Not both A and not-A.” A spoon cannot not be a spoon and a mountain cannot not be a mountain. This is not to say it is not possible to debate the height a collection of earth must be in order for it to be considered a mountain, or how round and deep the large end of a utensil must be in order for it to be considered a spoon, but only that once one has a clear idea of what such words refer to, it is not possibly to coherently assert that these words refer to non-spoons and non-mountains.
The third law of thought is the law of the excluded middle. Under this law, a thing must either have a particular attribute or not have that attribute. More specifically, a thing cannot have one attribute and a contradictory attribute at the same time and in the same manner. “Either A or not-A.” A spoon must either be round on the end or not round on the end. However, part of a spoon can be round and part of a spoon can be not-round, so it is possible to say that a spoon is both round and not-round, but not in the same manner.