Nietzsche was captured early on by Schopenhauer’s atheism and his anti-rational conception of the will, not reason (as had been argued by and large since the time of Socrates), as the driving force in the universe. Although Nietzsche would carry his philosophy far from the pessimistic, ascetic denial of the will that Schopenhauer advanced, Schopenhauer’s primal, driving will would remain a central element in Nietzsche’s thought. He envisaged this will specifically as the will to power and from this idea, derived a philosophy that was elitist and egoistic to the extreme.
Nietzsche’s will to power is embodied in one of the notions he is most famous for, the ubermensch (usually translated as ‘superman’ or ‘overman’), whom he sees as being a future, stronger generation of humans (he often refers to them as a new species) unafflicted by weakness such as pity, kindness, or equality. On the other hand, cruelty, violence, and war are to be valued as things which force the individual to test himself (Nietzsche didn’t have a particularly high opinion of women) and encourage competition to weed out those who are weak and sick, and therefore unfit to continue the species.
Nietzsche is well-known for his conceptions of master and slave morality, the former belonging to the noble, knightly-aristocratic warrior who creates (another key theme in Nietzsche) his own morals, defining ‘good’ and ‘bad’ (or ‘noble’ and ‘contemptible’) by what pleases him, rather than being held hostage to the latter, which finds perfect instantiation (according to Nietzsche) in the Judaeo-Christian religion.
Curiously, despite Nietzsche’s insistence on unadulterated, raw strength and power as the noblest of traits, a key and recurring theme in all of his books is gaity, lightheartedness, joy, dancing, and cheerfulness. In this aspect, more than any other he turned away from Schopenhauer’s pessimism and assertion that the will be snuffed out. Rather, Nietzsche advocated a carefree, Dionysian, abandon that revels in life. It is from this state of mind that he sees his ubermensch as being free to inflict cruelty and suffering on those weaker than them; not because they are trying to ‘get even’ or exact punishment for some grievance, but just because they can. I don’t think it would be an exaggeration to say that Nietzsche would say their cruelty is an ‘honest’ or even ‘innocent’ expression of their natural, exuberance as opposed to the scheming, manipulative duplicity that the priests in particular, peddle in, relying on concepts like guilt and sin, that directly inhibit the pure zest for life. The ubermensch take what they want in plain sight just because they can (think of a wild lion), whereas the priests get what they want through sneakily undermining their noble ‘betters,’ often out of a repugnant motive like revenge.
Nietzsche was fiercely atheistic and vocally criticised religions as promoting values that are in effect a denial of life. On the topic of religion, he is perhaps most famous for declaring that God is dead… and we are his murderers. With this, Nietzsche was highlighting what he saw as an impending crisis of morality which would hit as our increasingly secular society found the grounds of its morality, which he believed were founded on Christianity, undermined. In short, losing our belief in God means also losing the foundations of our morality.
Nietzsche is often criticised as promoting a stark, value-less world that inevitably leads to nihilism but in truth, he was anything but a nihilist. What he did was reject any school of thought that proposed absolute values we are all beholden to, as with Christianity, where becoming the perfect servant to God was perversely considered the ideal. His philosophy is not nihilistic because, rather than saying there are no values, he merely insists that they don’t come ready-made, instead we need to make our own.
I will mention one final feature in this brief outline of Nietzsche’s philosophy which, in my opinion, is often misunderstood. I am referring to his doctrine of eternal recurrence which first arises in The Gay Science and is posed as a test of one’s passion for life. He asks what you would say if you had to live your whole life again; all the joy and pain, the same events in the same sequence, for all eternity. Would you consider this a blessing or a curse? Only if you can affirm this doctrine have you lived life as Nietzsche feels it was supposed to be lived. Some commentators have interpreted this as a metaphysical reality that maybe Nietzsche believed was true. I can’t see any reason for suspecting this to be the case. He uses this doctrine to test one’s commitment to and thirst for life; the extent of the pure, primal relishing of life that Nietzsche valued so highly.