We’ll begin by discussing how means-end relations matter for what one ought, or has reason, to do or intend. (For an opinionated survey, see Kolodny 2018.) But we should first consider how “means” is understood. While “means” are often taken to be tools or resources, for our purposes, we will view means as actions, intentions, choices, decisions, etc. that might make use of such tools or resources.  It is natural to think of means to an end, so understood, as actions that help to cause the end to occur. But often philosophers count as means to an end whatever may help to bring it about. M may bring about E by causing it, as flicking this switch causes the illumination of this room, but M may also bring about E by helping to constitute it, as playing this measure partially constitutes the playing of this sonata, or fulfilling preconditions for it, as registering for this conference fulfills preconditions for attending it, or preventing things that might prevent it, as vaccination prevents disease that might prevent successful completion of the school year. Means are also often probabilistic.  Something may also count as a means to an end even if it is not guaranteed to help to bring about the end, but only has some chance of doing so.  Usage of “end” is also often ambiguous.  Sometimes “end” is used to refer to an action, such as the action of illuminating this room.  But sometimes “end” is used to refer to a state of affairs that is either desired or valuable, such as the state of affairs of this room’s being illuminated. We’ll here use “end” to refer to an action.