In my previous post I suggested, using amateur astronomy as an example, that an engagement in an activity can have a value over and beyond the value of the activity's goal, even though the value of the activity derives from the value of that goal.
An interesting instance of this is the following view of sex. Sex gets its value from being an activity naturally directed at offspring, offspring having great value. But the activity naturally directed at offspring has a value over and beyond that of offspring. Thus, even sex that does not result in reproduction, say because the couple is infertile (temporarily or permanently) has value. This value does not derive from the value of offspring in the particular case—there are none in the particular case—but from the fact that it is an instance of a type of activity that is directed at a good.
We can also see that there is something at least problematic in contraception. Contracepted sex is an engagement in a sexual activity while one is trying to ensure that that goal from which the activity derives its value is not attained. Imagine an amateur astronomer who, while engaging in the skilled activity of amateur astronomy (collimating telescope, choosing eyepieces, pointing telescope, etc.), just before looking in the eyepiece at the chosen object puts the lens cap back on. There, one's deliberate choices are contradicting that from which the activity derives its meaning.