It is probably true to say that the majority of philosophers have considered the universe to be mental. If the universe is really mental, it follows that matter cannot be quite real, and many philosophers have in fact brought forward cogent reasons for regarding matter as in some sense illusory. Those who hold this view are called Idealists. Idealism has historically assumed a number of different forms, between some of which there is little in common, but all forms of Idealism agree in maintaining that objects, such as chairs and tables, of which common sense believes the external world to exist, are not material.