Suppose I intend to rollerblade eight miles. And I succeed. Then I also rollerbladed three miles. But I need not have intended to rollerblade three miles, though of course my arithmetic is good enough that if asked “Will you also go three miles?” I would have answered affirmatively. Suppose that rollerblading three miles were intrinsically wrong. Then I couldn’t excuse myself by invoking the Principle of Double Effect, saying “I intended eight miles, not three.” Rollerblading three miles wasn’t intended. But it also wasn’t a side-effect like Double Effect talks about.
But isn’t rollerblading three miles a means to rollerblading eight miles? If it is, it isn’t a causal means (unless I have to rollerblade three miles before I’m allowed to do eight). Maybe it’s a constitutive means: rollerblading three miles is partly constitutive of rollerblading eight miles. But even that’s not quite right. There are many instances of rollerblading three miles within rollerblading eight miles: the first three miles, the last three miles, the middle three miles, and so on, perhaps even ad infinitum. One could make a case that rollerblading the first (or last or middle) three miles is a constitutive means to rollerblading eight. But rollerblading three miles is a disjunctive event: it is rollerblading the first three or the middle three or the last three or …. And while this disjunctive event has to happen for me to rollerblade eight miles, it isn’t a constitutive means to rollerblading eight miles.
So it looks like rollerblading three miles is neither a causal nor a constitutive means to rollerblading eight miles. This is another consideration in favor of my thesis that the Principle of Double Effect must go beyond the concept of means to that of accomplishment. For I definitely accomplish rollerblading three miles (in fact, multiple times) in rollerblading eight miles. Here's a quick test for this: Suppose that after three miles I have to stop. Then I would say: "I aimed for eight miles but all I managed to accomplish was three." But if I didn't stop after three, I would surely still have accomplished three.