Kant famously says that only one thing is good without qualification — a good will. We are to judge a person’s moral worth not primarily by what they do but by what they will.
We can of course understand the moral importance of a good will. Kant is capturing a broadly held intuition in proposing a view, for example, in accordance with which a shoe store owner is not considered moral who would like to charge a higher price for a pair of shoes than the shoes are worth, but doesn’t do so only because there is a competing store nearby and he will lose the business to his competitor if his prices are too high. This shoe store owner may well do the right thing. But it is not hard to see why Kant would say that this isn’t sufficient for us to judge the shoe shop owner as moral. Here, it is not the shoe shop owner’s goodness that prevents him here from doing something bad. Rather, it is merely the coincidence of having a competitor nearby that prevents him from price gouging his customers. Opportunity is all that stands in the way of this shoe shop owner doing the wrong thing.
This example does seem to capture part of what Kant is getting at in his discussion of good will. Yet this doesn’t fully capture Kant’s sense of things. For, in Kant’s view, someone might have good intention but still not have a good will. In order to have a good will, in Kant’s view, one needs a rationally formed will — that is, one needs to be operating on a principle that can pass Kant’s test of rationality. It must be universalizable.
Perhaps the following can make the difference clearer: A consequentialist could feasibly fail to repay a loan to someone who is wealthy because she has decided that the most moral use of the money is to help the needy rather than give back the borrowed money to the wealthy person. She might even do this solely with the good intention of helping the needy and with no malice toward the person who lent her the money. Yet for Kant, this good intention would not indicate a good will. To have a good will, this person would need to act on a principle that is allowed by the categorical imperative. And in sync with the categorical imperative, she would need to pay back her loans, since, in Kant’s view we cannot universalize the principle that we break promises and not pay back our debts. (For more on the categorical imperative, see the linked post.)
Good intention (depending on further definitions) may play a role in Kant’s view of a good will. But it is not the same. It is at best a necessary but insufficient condition.