Soon after this passage, Hume is careful to note that it wouldn’t be one’s intending of means insufficient for one’s ends that’s unreasonable, but the false belief on which this intention is based.  For example, when I falsely believe that staying on 95N will get me to Memphis, which is where I intend to go, and so I intend to stay on 95N, it’s my belief that 95N will get me to Memphis that’s unreasonable, not the intention, based on this belief, to stay on 95N.