Friday, May 17, 2024

Acting for the sake of rationality alone

Alice is confused about the nature of practical rationality and asks wrong philosopher about it. She is given this advice:

  1. For each of your options consider all the potential pleasures and pains for you that could result from the option. Quantify them on a single scale, multiply them by their probabilities, and add them up. Go for the option where the resulting number is biggest.

Some time later, Alice goes to a restaurant and follows the advice to the letter. After spending several hours pouring over the menu and performing back-of-the-envelope calculations she orders and eats the kale and salmon salad.

Traditional decision theory will try to explain Alice’s action in terms of ends and means. What is her end? The obvious guess is that it’s pleasure. But that need not be correct. Alice may not care at all about pleasure. She just cares about doing the action that maximizes the sum of pleasure quantities multiplied by their probabilities. She may not even know that this sum is an “expected value”. It’s just a formula, and she is simply relying on an expert’s opinion as to what formula to use. (If we want to, we could suppose the philosopher gives Alice a logically equivalent formula that was so complicated that she can’t tell that she is maximizing expected pleasure.)

I suppose the right end-means analysis of Alice’s action would be something like this:

  • End: Act rationally.

  • Means: Perform an action that maximizes the sum of products of pleasures and probabilities.

The means is constitutive rather than causal. In this case, there is no causal means that I can see. (Alice may have been misinformed by the same philosopher that there is no such thing as causation.)

The example thus shows that there can be cases of action where one’s aim is simply to act rationally, where one isn’t aiming at any other end. These may be defective cases, but they are nonetheless possible.

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