name, "circular cup" or two daughters that have in common being the female offsprings of Frank. There are many such properties, such as being human, red, male or female, liquid, big or small, taller than, father of, etc. While philosophers agree that human beings talk and think about properties, they disagree on whether these universals exist in reality or merely in thought, speech and sight. Principle of individuation Related to the problem of universals, the principle of individuation is what individuates universals. Sorites paradox Otherwise known as the "paradox of the heap", the question regards how one defines a "thing." Is a bale of hay still a bale of hay if you remove one straw? If so, is it still a bale of hay if you remove another straw? If you continue this way, you will eventually deplete the entire bale of hay, and the question is: at what point is it no longer a bale of hay? While this may initially seem like a superficial problem, it penetrates to fundamental issues regarding how we define objects. This is similar to Theseus' paradox and the continuum fallacy. Theseus paradox Also known as the ship of Theseus, this is a classical paradox on the first branch of metaphysics, ontology (philosophy of existence and identity). The paradox runs thus: There used to be the great ship of Theseus which was made out of, say, 100 parts. Each part has a single corresponding replacement part in the ship's port. Over the centuries, each part is replaced individually as it breaks, and eventually, not a single original part of the ship remains. Is this new ship the ship of Theseus or not? If yes, consider this: the broken original parts are repaired and re-assembled. Is this the ship of Theseus or not? If not, let us name the new ship "The Argo". At what point did the crew of the Theseus become the crew of the Argo? And what ship is sailing when 50 of the parts have been replaced? If both the ships trade a single piece, are they still the same ships? This paradox is a minor variation of the Sorites Paradox above, and has many variations itself. Both sides of the paradox have convincing arguments and counter-arguments, though no one is close to proving it completely. Material implication People have a rather clear idea of what if-then means. In formal logic