Q. Is it a mortal sin when I don’t help homeless people I see on the street? I work in a city where I see homeless people a lot. Recently, I saw a homeless woman I’ve seen a few times and felt the urge to buy her some food. I thought about doing it but ultimately I didn’t and decided to just go home instead. Was this a mortal sin? —Gabriel, Sydney, Australia

A. The Catholic Church teaches that for a sin to be mortal three things are necessary.

First, an action we are contemplating needs to be really bad (called grave matter). Second, we need to know pretty clearly that it is really bad (called full knowledge). And third, we need to be free when we choose it — that is, free not to do it and then still do it (called complete consent). (See Catechism of Catholic Church 1857).

In a city such as Sydney (or any large city in the U.S. or Europe), homeless people have a variety of social services available to them for assistance. The men and women we see on our street corners do not rely upon our one-off benefactions for their subsistence. If they did, then our responsibility for their welfare would be much, much greater. As it is, it is unlikely that the choice not to feed a poor man fulfills the conditions for mortal sin.

I say choice, because that seems to be what’s described above, not merely an oversight. (Gabriel says he “decided” to go home.)

Now choices can be motivated by many things. You might be afraid for your safety, or have no money in your pocket, or be late for a doctor’s appointment. Or when you see the homeless person, you might call to mind your community’s social safety net, and decide that your help isn’t necessary. In these instances, there need be no sin at all.

But sometimes we do nothing, not from fear, lack of money, busyness, etc., but out of indifference.

I am using “indifference” here with a decidedly negative connotation. So I do not mean it, as one might, who says, when asked whether he likes the color of a blouse, “I am indifferent,” meaning he has no opinion.

Here I use indifference to mean “not being interested in” or “not caring” or “showing no concern about” something that matters.

This kind of indifference, I will presume, is always wrong to some degree — wrong in a small way if I am indifferent to minor matters, wrong in a grave way if I am indifferent to serious matters.

The welfare of the poor is always a serious matter. This is why sacred Scripture insists that indifference to the poor is gravely wrong. Think, for example, of the parable of Lazarus and the rich man (Luke 16:19-31). We know the rich man sees the needy man at his gate, because he knows his name; from Hades he specifically asks Abraham to “send Lazarus” to dip his finger in cool water to soothe his tongue.

The problem is that he is indifferent to Lazarus, feels nothing for the beggar, and does nothing to help him. Because of the rich man’s punishment, we must presume he made no effort to stir up empathy, to change himself — as good people do — to overcome his moral weakness.

Is the rich man’s indifference mortally sinful? Scripture thinks so. The Gospel says when he dies, he goes to “Hades” where he is “tormented.”

One might object saying the situation in ancient Palestine is much different from today; that there was no welfare state, no soup kitchens, no homeless shelters and no ERs where the poor could get basic medical care; and there is certainly nobody like Lazarus lying at our gates!

I agree with this much: There is likely no Lazarus lying at our front door.

But the globe today is covered with places like ancient Palestine — places where the poor must scrape together their daily bread, and some days have no bread at all, and the nearest public shelter or sandwich line are a continent away. Like the rich man, we know they’re there, because we see them every day, on the news. We feel disquieted. We know we might help, at least in a small way.

And so all people are faced with morally consequential alternatives: turn a deaf ear to the disquiet we feel and go on with our lives, or do something.

What should we do? Scripture, Tradition, and Catholic Social Teaching converge on this general point: We should do all we reasonably can to assist those in need, especially those in grave need.

For some of us, $10 in the weekly collection basket is what we can do. For others, $10 in the basket masks culpable indifference.

We should ask ourselves: Am I doing all I reasonably can?

And we should pray: Jesus, give me a heart of compassion for the poor, and guide me in making good decisions about caring for their needs.

For more on our duties to the poor, see “We Are Our Brothers’ Keepers.”