  These look contradictory, but need not be in any way inconsistent: (a) may be true in that working in a bar is the only way through which you can manage to get drunk every evening; (b) may be true in that, given that you are a potential alcoholic with a weak will, not working in a bar is a necessary condition of your maintaining your health (which you either are much concerned about, or ought to be). We can distinguish (a) and (b) most clearly by asking how to detach the consequent. This seems straightforward in the case of (b): one can detach “You shouldn’t work in a bar” from (b) by asserting “You (do) want to get drunk every evening”. But how, if at all, can we detach the consequent of (a)?  