According to Spinoza’s report, the Stoics held that the affects depend absolutely on our will and can be placed under its complete command.

The preface to Part V announces an inquiry into the power of reason: what can reason do about the affects? Absolute mastery has already been denied. Even the Stoics, Spinoza says, had to acknowledge how much practice and effort restraint requires. Experience forced the concession, rather than their principles.

Someone tried to illustrate the point with two dogs—unless he remembers wrongly. A house dog and a hunting dog were trained until one took to hunting while the other stopped pursuing hares. The memory qualification is there in the telling.

As far as I can gather

Spinoza next sets out Descartes’ position at some length, referring to Part I of The Passions of the Soul. The mind is especially joined to a small gland in the brain, the pineal gland, whose movements it can direct through willing.

Different movements are naturally connected with different thoughts, but habit can establish other associations. From this Descartes concludes that even a weak soul, properly guided, can gain absolute power over its passions.

That, Spinoza says, is the distinguished philosopher’s view, as far as he can gather from Descartes’ own words. Were it not so ingenious, he could scarcely believe so great a man had proposed it.

Then the criticism begins. Here is a philosopher committed to deducing only from self-evident principles and affirming only what is clearly and distinctly perceived. He criticizes the scholastics for explaining obscurity through occult qualities. Yet he adopts a hypothesis which Spinoza finds more occult than any of them.

I should like to ask

What does Descartes understand by the union of mind and body? What clear and distinct conception does he possess of a thought joined intimately to a little quantity of matter? Spinoza wants the union explained through its proximate cause.

Descartes has separated the mind so thoroughly from the body, he argues, that no particular cause explains their union. The explanation must appeal instead to the cause of the whole universe: God.

Spinoza also asks how much motion the mind can impart to the gland, and with what force it can hold it suspended. He says he does not know whether the mind turns it more slowly or quickly than the animal spirits do. He disputes the proposed anatomy and passes over the doctrine of free will, whose falsity he believes he has already demonstrated.

The opening challenge invokes Descartes’ own stated standard. In setting out other people’s positions, however, Spinoza has twice marked a limit on his own report: unless I remember wrongly; as far as I can gather from the words.

Those qualifications do not prove the account correct. They tell the reader what kind of claim the critic is making.

At a meeting

Someone gives a figure in a meeting. Another person corrects it: unless I remember wrongly, last quarter’s figure was three hundred and twenty.

The correction rests on memory. In that ordinary phrase, the speaker has said so.

One can challenge another person without making one’s own recollection sound like a document already checked.

At the end

Spinoza now proposes to determine remedies for the affects through knowledge of the mind alone.

He believes, he says, that everyone has experienced such remedies, though without observing them accurately or seeing them distinctly.

The preface ends by pointing the inquiry toward something readers may already have lived, but not yet examined.