Nietzsche devotes a lot of his intellectual energy to exposing and attacking what he takes to be the philosophers’ naive trust in immediate certainties: the ‘I’ that thinks, the ‘I’ that wills and considers itself a miraculous causa sui, and so on.

His theory of will to power is designed to work against these immediate certainties even though it itself sounds like an immediate certainty.

In Human, All too Human, published in 1878 Nietzsche had declared that all is representation and that no intuition can take us any further. From this it follows for him that all is to be understood in terms of mechanical necessity and causal determinism.

Ethics (practical reason) is thrown out of the window at this point in his thinking and the imperative is simply ‘do not judge but be just’. Nietzsche is not yet ‘anti-Christ’; on the contrary, this Nietzsche says we should imitate Christ!

By the time of Beyond Good and Evil (1886) we have a quite different Nietzsche. There is not only representation; there is not simply mechanical necessity and causal determinism.

There is also the will to power, or the mechanical or material world seen from inside. The will to power for Nietzsche is the ‘primary’ cause of all things, the real cause, and it is a pathos (feeling), the most primal or primordial affect there is.

On the face of it, the will to power sounds completely and utterly human: what is more ‘human’ than to say that people want power?

The difficulty is that Nietzsche is not saying this, but trying to develop a theory or doctrine that goes against our ingrained habits of representation and valuation.

Nietzsche develops the will to power as a doctrine of psychology, physiology, morphology, and evolution, but in no sense is this to be understood in terms of a theory of human psychology which would give us the cardinal drive of human agency in terms of a subject (and I or ego: ‘will’) wanting an object it lacks, ‘power’.

This is what we have to try and think, and it is very difficult. It is difficult because of language: as Nietzsche says, we will not get rid of God until we get rid of grammar.

He holds that an appeal to something like the will to power needs to be made owing to the deficiencies of mechanism.

Mechanical events, he argues, are active only to the extent that energy is a feature of them, and, moreover, this energy cannot simply be construed as the effect of matter but only of ‘will’ (the will to life which is a will to power conceived as an insatiable desire to manifest power, a creative drive for growth and expansion, a releasing of force or energy, and so on).

This is not a monism but a radical pluralism. The will to power is essentially a principle of the synthesis of forces, functioning as a plastic principle in the sense that it is no wider than what it conditions, never separable from particular determined forces or from their quantities, qualities, and directions. It is always plastic and changing.

The fundamental prejudice of natural science is to think it has understood and explained the world when it has broken it down into discrete components such as atomic, quantifiable units.

But the idea that only a scientific (mechanistic) approach can comprehend the 'meaning' of things on account of its ability to calculate and weigh things, to see and touch them is, Nietzsche says, 'a crudity and naiveté, assuming that it is not a mental illness, an idiocy'.

A purely quantitative world – which is what mechanism gives us - would be 'rigid, unmoving, dead'.

Nietzsche is not seeking to restore the discredited idea of purpose or teleology. His point is rather that the world cannot be explained solely on the basis of a hypothesis which posits entirely passive events (all atomic motions and combinations are caused by impact from other atoms that happen to move).

This is to deprive natural events of sense or meaning, like reducing music to formulas and then claiming that on this basis we can ‘comprehend’ music.

Our habit of thinking in terms of a subject or ego is partly a result of the habit we have of taking a 'mnemonic' (an abbreviated formula) to be denoting a real entity and as a cause of action as when we say of lightning 'it flashes'; we do the same with the fiction of the will, the belief that every activity presupposes an agent (as something essential that does not vanish in the multiplicity of change).

When we speak of substances and faculties – the Ego, the Will, etc – we are engaged in fabrication. We are distorting and simplifying processes and events that are much more complex than our categories and established modes of thinking enable us to appreciate.

Nietzsche proposes we make the body and physiology the starting-point instead: “Essential to start from the body and use it as a guiding thread. It is the far richer phenomenon, and can be observed more distinctly”. The body has evolved in terms of “a prodigious alliance of living beings”.

It is a magnificent binding together of the most diverse life, the ordering and arrangement of the higher and lower activities, a thousand-fold obedience which is not blind, even less mechanical, but a shrewd, selecting, considerate, even resistant obedience.

Measured by intellectual standards, this whole phenomenon “body” is as superior to our consciousness, our “mind”, our conscious thinking, feeling, willing, as algebra is superior to the times tables.

Every living thing strives to be and become what it is: an augmentation of power in which pleasure is simply the symptom of the feeling of power achieved, or a consciousness of difference.

It is not really happiness we seek, for Nietzsche, but rather the pleasure to be had from power, that is, mastery and the overcoming of obstacles and resistances. Compared to the pre-human Nietzsche thinks that the human represents a tremendous quantum of power, not an increment of happiness.

Nietzsche thinks that the doctrine of the will to power has an intellectual integrity lacking in other accounts of the world: it probes deeper, it doesn’t offer a conception of the world and ourselves that will flatter us or appeal to our vanity.

Furthermore, something like the will to power can enable us to think ‘beyond good and evil’, that is, outside the simple-mindedness of moral judgement and moral fanaticism, allowing for a much richer – and more honest - appreciation of the economy of life and the full range of human affects that have made the human animal what it is.