<Li> Some Greeks are logicians and some logicians are tiresome; therefore, some Greeks are tiresome . Invalid argument: the tiresome logicians might all be Romans (for example). </Li> <Li> Either we are all doomed or we are all saved; we are not all saved; therefore, we are all doomed . Valid argument; the premises entail the conclusion . (Remember that this does not mean the conclusion has to be true; it is only true if the premises are true, which they may not be!) </Li> <Li> Some men are hawkers . Some hawkers are rich . Therefore, some men are rich . Invalid argument . This can be easier seen by giving a counter-example with the same argument form: <Ul> <Li> Some people are herbivores . Some herbivores are zebras . Therefore, some people are zebras . Invalid argument, as it is possible that the premises be true and the conclusion false . </Li> </Ul> </Li> <Ul> <Li> Some people are herbivores . Some herbivores are zebras . Therefore, some people are zebras . Invalid argument, as it is possible that the premises be true and the conclusion false . </Li> </Ul>

There are some series of statements that fail to make an argument