Whoever wills the end, wills (so far as reason has decisive influence on his actions) also the means that are indispensably necessary to his actions and that lie in his power.

In other words:

For all A:
If reason has decisive influence on A, then
    for all E
    (if A wills end E, then
       for all M
       (if (M is a means to A) and
       (M is indispensably necessary to E) and
       (M is in A's power), then
          A wills M)).