(This marks the sixth of eleven "meetings" of our virtual reading group on Derek Parfit’s Climbing the Mountain—see here for further details. Next week, we will discuss Chapter 8 of the June 7th version of the manuscript, which can be found here.)
According to Kant, the Greatest Good would be a world in which everyone was wholly virtuous and had all the happiness that they deserve. Furthermore, Kant tells us, "Everyone ought to strive to promote the Greatest Good." In making this latter claim, it may seem that Kant is guilty of the same fundamental error that he accused the ancient Greeks of making: trying to derive the moral law from their beliefs about the Greatest Good. Kant, however, doesn’t make this error, for, as Parfit suggests, Kant uses the phrase ‘the Greatest Good’ to mean ‘what we ought to strive to promote’. Since, for Kant, the thought that we ought to strive to promote universal virtue and deserved happiness is prior to the thought that the Greatest Good would be a world of universal virtue and maximal deserved happiness, he is not deriving the moral law from his beliefs about the Greatest Good.
Now it might seem that all we need is Kant’s Formula of the Greatest Good to tell us what to do, but this would be a mistake. We need to know how to promote the Greatest Good. According to Kant, we do so by following the moral law, as described by his other formulas. Thus Kant believes that by following the moral law we can each do our best to promote universal virtue and deserved happiness. This may be surprising given that Kant believes that we ought to follow strict rules that prohibit, for instance, lying even to an enquiring murderer. How could adhering to such strict rules be the best way of striving to promote the Greatest Good? The answer lies with the widely held and fairly plausible assumption that people are more likely to succeed in, say, promoting other people’s (deserved) happiness by following certain rules than by aiming at that end itself. This explains, Parfit suggests, why Kant believes that following his various formulas (e.g., the Formula of Humanity) is the best way to strive to promote the Greatest Good.
This part of Kant’s view overlaps with one version of act-consequentialism. On this version of act-consequentialism, it is held both (1) that everyone ought to produce the greatest amount of good and (2) that the act that produces the greatest amount of good is the one belonging to the "set of acts, done by us at different times or done by different people, that would together produce the best effects." According to (2), determining the goodness produced by a particular act—say, that of keeping a certain promise—requires us not only to consider the effects that this particular act has but also the effects that the general practice of promise-keeping has, for part of this particular act’s goodness consists in its share of that total amount of goodness produced by the general practice of promise-keeping. So even when keeping a promise would itself have bad effects, its total goodness (consisting of its share of the good that the general practice of promise-keeping does minus the bad effects that it itself has) will be greater than the alternative. Thus, if the act-consequentialist accepts (2), or what Parfit calls "the Whole Scheme View," then she will, like Kant, hold that it is by following certain strict rules, such as "Always keep one’s promises," that one can best strive to promote the greatest good.
In deciding whether we ought to accept this part of Kant’s view (viz., that by following the moral law, as described by Kant’s other formulas, everyone could best promote the ideal world), we’ll need to answer the following two questions:
Q1: "Ought we always to strive to promote a world of universal virtue and deserved happiness."
Q2: "Is it by following Kant’s other formulas that we can best promote this ideal world?"
We cannot fully answer Q1 until we have answered Q2, and we can’t yet answer Q2, for we still have yet to consider Kant’s other main formula: his Formula of Universal Law, which is the topic of next week’s chapter.