And given this systematic dependence, it is extremely difficult to imagine the nature of the mind process independently of the self, although from an evolutionary perspective, it is apparent that plain mind processes preceded self processes.

However, given that the self is our only natural means to know the mind, we are entirely dependent on the self's presence, capabilities, and limits.

We are now at a stage where we can draw up a list of these changes and conceive treatments to slow or reverse each of them.

These phenomena impact every part of us - from genes and molecules to cells and whole systems inside our body — and go on to cause the aches and pains, worsening sight, wrinkles and diseases of the elderly.

Making matters worse, when cancer is exposed to chemotherapy, drug-resistant mutants can escape. In other words, just as resistant strains of bacteria can result from antibiotic use, anticancer drugs can produce resistant cancer cells.

Every time a new generation of cancer cells is born, those cells harbor new mutations that go beyond those already present in the genes that are supposed to regulate growth.

it's about another critical characteristic that embodies cancer: its ability to evolve over time. Although people like to envision cancer as a static mad cellular copying ma-chine, it's much more clever and dynamic than that.

As the viewer moves around, the face seems to follow - and not in the weak, unconvincing sense that the Mona Lisa's eyes are said to follow you. The hollow mask really really looks as though it is moving.

What is surprising is that, when seen from behind - the hollow side - it also looks like a solid face, and our perception of it is very odd indeed.

Of these, scientists believe that about half are synonyms - those described more than once and so having two or more names, in which case only the first description and name is considered legitimate. This leaves a total of 1.8 million 'valid' species.