James Sully, answered from the texts and cited to the page.
The pessimists — Schopenhauer, and von Hartmann after him — build a whole metaphysics of despair on a psychological claim: that pain outweighs pleasure in human life, that satisfaction is merely the brief cessation of want, and that existence is therefore a bad bargain not worth the making.12 I have examined this claim as a psychologist must, and I find it does not bear the empirical weight laid on it.
The reckoning of pleasures and pains is far more intricate than the pessimist allows; he undervalues the great mass of quiet, positive, unnoticed satisfactions that make up the healthy texture of ordinary life, and overvalues the vivid pains that stand out in memory. The pessimist's hedonic calculus is a bad calculus, resting on introspective errors of just the kind I have catalogued elsewhere.
I do not preach a shallow optimism; life has real suffering, and I grant the pessimist his seriousness. But the sweeping verdict that existence is on balance an evil is not a finding of sober psychology; it is a mood raised to a metaphysic, and the empirical study of feeling does not sustain it.34
Now this desire in the case of a pain increases the primary impulse to rid oneself of the pain, and so helps to make this cessation of a painful condition doubly a relief. In the case of pleasure, however, the desire for relief counteracts the primary impulse to retain the pleasure, and so tends to make the cessation of a pleasure a painless and neutral condition.Pessimism A History and a Criticism, pp. 133–135
It is now time to pass to Hartmann's estimate of the value of life as deduced from his metaphysical principles, and as confirmed by induction from observable facts. Like Schopenhauer, Hartmann views life from the standpoint of hedonism, measuring all its value in terms of pleasure and pain. Existence is essentially incomplete, irrational, and a huge blunder.Pessimism A History and a Criticism, pp. 131–132
Lastly, the pessimists' theory of desire, by confounding, desire with volition, mixes the distinctly pleasurable state of ^ anticipation during the execution of a volition or series of volitions with the conflicting and painful state of desire proper. How this fallacy helps them in proving their pessimism need hardly be pointed out.Pessimism A History and a Criticism, pp. 217–218
It is really impossible to deal quite seriously with this part of Hartma nn's argument. There is a naivete in this extension of the doctrine of chances to such a remote ontological problem which produces a distinctly comical effect. A man who can draw comfort out of such shadowy material is plainly not destined to be a pessimist.Pessimism A History and a Criticism, pp. 181–182
Sully's Pessimism was an early and respected critical engagement with Schopenhauer and von Hartmann, notable for turning an empirical psychological analysis of pleasure and pain against a metaphysical doctrine. The substantive question — whether life contains a favorable balance of pleasure over pain — is now pursued by the psychology of well-being, and several of Sully's points anticipate modern findings: hedonic adaptation, the salience bias of painful memories, the large role of ordinary low-level positive affect, and the unreliability of the intuitive hedonic calculus. The debate between optimistic and pessimistic readings of the human hedonic balance remains open (Benatar's modern antinatalist pessimism revives it), but Sully's empirical, anti-metaphysical way of conducting it is broadly the modern one.