The motivation of living creatures does got boil down to any single basic force, not even an 'instinct of self-preservation.' It is a complex pattern… - Mary Midgley

Creatures really have divergent and conflicting desires. Their distinct motives are not (usually) wishes for survival or for means-to-survival, but for various particular things to be done and obtained while surviving. And these can always conflict. Motivation is fundamentally plural. It must be so because, in evolution, all sorts of contingincies and needs arise, calling for all sorts of different responses. An obsessive creature, constantly dominated by one kind of motive, would not survive.

Let us start by considering why the attempt to glorify science on its own cannot work. This is because human thought operates as a whole. It is an ecosphere, a vast and complex landscape, including, but not confined to, common sense. Science itself is, of course, not a single compartment but a large, thickly wooded area comprising many sciences, an area that merges into those around it. Those sciences vary from physics to anthropology and all of them are shot through with problems coming from areas outside them, such as philosophy and history. Biology, for instance, has to deal with philosophical problems about the concept of life and also with vast historical problems about evolution for which it uses historical methods, not those of physics.

Still, people have a lot of obvious and important things that other species do not–speech, rationality, culture and the rest. Comparison must deal with these. I have tried to discuss some of the most important of them, not attempting at all to deny their uniqueness, but merely to grasp how they occur in what is, after a primate species, not a brand of machine or a type of disembodied spirit. I have tried to show these capabilites as continuous with our animal nature, connected with our basic structure of motives.

Scientism exalts the idea of science on its own, causing people to become fixated on the assumptions that seemed scientific to them during their formative years. This prevents them from seeing contrary facts, however glaring they may be, that have been noticed more lately.