Such conditions or expectations would not be wrong when giving money to a friend or colleague. Seeing the holes in her shabby sweater, you might give her some money and ask her to buy a new sweater with it. And you would then expect that, if she accepts the gift, she will use it the way you stipulated.

So why should matters be different with a homeless person? The obvious answer is: because you owe him support. OK, you don't owe support to every homeless person, but you do have an obligation to do something to support some of them. And because it's an obligation, you may not attach conditions or expectations -- just as, when you own money to your landlady, you may not attach conditions or expectations regarding how she should spend your payment.

I am not convinced by this line of argument. I accept that we have an obligation to support the homeless. This includes an obligation to help them meet their basic needs (esp. when our society is doing too little on this score). But it does not include an obligation to help them get an MP3 player, a blackberry, a margarita or a joint. It is perfectly alright, then, that you attach a condition or expectation to your payment, asking that it be used to fulfill your obligation to help meet basic needs rather than for some other purpose.