Not pessimistic but empirical. The Buddha approached suffering the way a physician approaches an illness: here is the condition, here is its cause, here is the prognosis, here is the treatment. The four noble truths are that consultation written down. They were the first thing he taught after his awakening, in the deer park at Sarnath, and everything else in the tradition unfolds from them the way a course of treatment unfolds from a diagnosis.
The frame matters as much as the content. A physician does not ask you to believe in a diagnosis; she asks you to check it against your symptoms and take the treatment seriously enough to try it. The four truths are offered the same way. Nothing here has to be accepted on authority. Each is a claim about how experience behaves, and each is tested in the only laboratory available, which is your own life.
The diagnosis — Dukkha
The first truth: dukkha exists. The word is usually translated "suffering", and that is true but slightly too loud. Dukkha covers the whole register, from grief and pain at one end to something much quieter at the other: unsatisfactoriness, the restlessness built into everything that depends on conditions, which is everything we can point to. One traditional gloss, more picture than philology, hears in the word an axle that does not sit true in its wheel. The cart still moves; nothing about the ride ever quite settles.
The teaching sorts this ache into three layers. There is plain pain: illness, loss, the body wearing out. There is the ache of change: everything pleasant is on a timer, and some part of you knows it even on the last good morning of the holiday. And there is the subtlest layer, the one the first two hide: even the good thing, fully arrived and held in both hands, does not finally settle the mind that holds it. This is dukkha as one of the three marks of existence, stamped on everything that arises and passes; its place beside impermanence and non-self is treated there.
None of this is a doctrine of misery. The Buddha was not arguing that life contains no joy; he was refusing to look away from the ache that most lives spend enormous energy not noticing. A diagnosis is not pessimism. It is the first step of a cure.
The cause — Tanha
The second truth: dukkha has a cause, and the cause is tanha, literally thirst. Craving is not the same thing as wanting. It is the lean inside the wanting, the mind tipping out of the present toward the next thing, certain that the next thing is where the settling will finally happen. And what thirst catches, clinging (upadana) keeps: the craving hardens into a fist around whatever it caught.
Watch the loop run once and you have verified the second truth. You want, you get, the satisfaction quietly resets, the wanting re-arms. Modern psychology has measured that reset and calls it the hedonic treadmill: gains are absorbed, the baseline recovers, and the thirst that promised to be final turns out to be renewable.
Notice what the diagnosis does not say. It does not say desire is the enemy, and the treatment is not the extinction of wanting. You can love people, choose work, build things. The target is the thirst behind the wanting, the part that insists peace is on the far side of the next acquisition, because that part has been wrong every single time. Yoga trains the same loosening under the name Contentment (Santosha): wanting held lightly, from a ground that is already enough.
The prognosis — Nirodha
The third truth is the reason the teaching exists at all: this can end. Nirodha means cessation, and the logic is a physician's logic. A condition with a cause is not a fate; what arises when its cause is present can cease when its cause is removed. Thirst is not the weather of the mind, it is a process the mind runs, and a process can be unlearned. Cessation is not the end of experience, and not the end of you. It is the fever breaking. The tradition's name for the cool freedom on the far side is nibbana, and on this site its full treatment sits with the eighth limb, absorption (Samadhi): one tradition's name for the same clear ground.
A modern saying, often placed in the Buddha's mouth though it appears nowhere in the early texts, catches the prognosis exactly. Asked what he had gained from meditation, the teacher replies: "Nothing. But let me tell you what I have lost: anger, anxiety, depression, insecurity, fear of old age and death." Not his words, but faithful to his teaching. The cure is measured in what falls away.
The treatment — Magga
The fourth truth is the prescription: there is a path, magga, that leads from the second truth to the third, and it has eight factors. The path has its own page, the noble eightfold path, and this page only needs to say what kind of thing it is. It is not a creed to adopt on the strength of the first three truths. It is a course of treatment, and a course of treatment works only if taken; a diagnosis you merely agree with changes nothing.
Patanjali drew his own map of what drives suffering: the five afflictions, the kleshas, with craving (raga) among them and unclear seeing at the root. The two maps rhyme closely, down to the shared conviction that the afflictions are removable, and the parallel is drawn out on the kleshas page.
The middle path
The path the Buddha taught runs between two extremes: self-indulgence on one side, self-mortification on the other. One binds you to craving; the other wears down the body and mind you practise with. He knew both from the inside, having spent years in near-starvation among the forest ascetics and found it produced weakness, not wisdom. The sustainable way runs between them, and it is this middle way the eightfold path maps. Aristotle's golden mean arrives at the same disciplined centre from a different direction, and the whole question of how far to go, including the tradition that took the extreme road, is drawn out on the cross-tradition map.