When Cardinal Joseph Ratzinger sent out a brief memo in June about politicians and Communion, he probably never imagined it would ignite a heated discussion about Catholics and voting.

The document, leaked to an Italian reporter but never officially acknowledged by the Vatican, focused on the grounds for denying Communion to pro-abortion Catholic politicians.

Almost as an afterthought, it added two sentences about Catholic voters:

First, it said, a Catholic who deliberately voted for a candidate precisely because of the candidate's pro-abortion (or pro-euthanasia) stand would be guilty of "formal cooperation in evil" and should exclude himself from receiving Communion.

Second, when a Catholic does not share a candidate's stand in favor of abortion but votes for that candidate for other reasons, it is considered "remote material cooperation," which is "permitted in the presence of proportionate reasons."

Reaction to those two sentences has been simmering all summer, fueled in part by election-year politics.

One self-styled "traditional" Catholic publication criticized Cardinal Ratzinger, who heads the Congregation for the Doctrine of the Faith, saying his words would be taken as a "license to vote for pro-abortion politicians."

In a New York Daily News column headlined "Catholics can vote for Kerry," Father Andrew Greeley said Cardinal Ratzinger had correctly underlined that Catholics should not be single-issue voters, but should weigh all the issues.

Other conservative Catholic Web sites have criticized Father Greeley's column and disputed the idea that Cardinal Ratzinger has given a green -- or at least yellow -- light to Catholic voters who intend to vote for pro-abortion candidates.

At the Vatican, officials are dismayed for several reasons, starting with the fact that a private communication was leaked. Moreover, they say, the ensuing discussion has mixed up two very different issues -- the public actions of Catholic politicians and the private moral decisions faced by Catholic voters.

Vatican officials also are concerned that the discussion of "leeway" in voting for pro-abortion candidates may eclipse a more important point Pope John Paul II and others have been hammering home for years: That Catholics are morally obligated to try to limit the evil of abortion and euthanasia, and that those life-and-death issues should have unique moral weight with Catholic voters.

The one-page memo that started the discussion was sent with a letter from Cardinal Ratzinger to Cardinal Theodore E. McCarrick of Washington, who heads the U.S. bishops' Task Force on Catholic Bishops and Catholic Politicians. Sources described the memo as an unsigned "staff document" aimed at summarizing basic principles. They said it did not begin to explore the complexity of the issue of voting and sin, which, in the words of one official, is pretty much "terra incognita" for moral theologians.

"The memo was certainly not intended to clear the way for Catholics to vote for candidates who are in favor of laws permitting abortion or euthanasia, but rather to clarify that the simple act of voting for such candidates might not per se justify one's exclusion from Holy Communion," said U.S. Dominican Father Augustine DiNoia, undersecretary of the Vatican's doctrinal congregation.

The problem is that it's difficult to determine the purpose, or "moral object," of an act of voting, Father DiNoia said.

"The only thing we could say is, a person might come to be in the state of mortal sin and therefore unworthy to receive Communion if they voted precisely with the moral object of extending abortion or the provision of abortion," he said.

"But that would be the only case where that would happen," he said.

For the church, there's no question about the sinfulness of abortion, but there are serious questions about how far culpability extends beyond those directly involved in abortion.

That's where the concepts of "formal" and "material" cooperation come in. These are traditional terms in theology, although their application to the act of voting is quite new.

Cooperation in evil concerns people who are drawn into the bad act of another person. In general, "formal" cooperation means culpability, whereas "material" cooperation --- being more remote --- does not, Father DiNoia said.

In the case of abortion, the church considers as the principal agents the person procuring it and the doctor performing it. In his 1995 encyclical, "Evangelium Vitae," Pope John Paul II spoke at length about cooperation in acts against human life -- but did not mention voting.

"Christians, like all people of good will, are called upon under grave obligation of conscience not to cooperate formally in practices which, even if permitted by civil legislation, are contrary to God's law," the pope said.

"Such cooperation occurs when an action, either by its very nature or by the form it takes in a concrete situation, can be defined as a direct participation in an act against innocent human life or a sharing in the immoral intention of the person committing it," he said.

The recent doctrinal memo's mention of "proportionate reasons" has led some people to suggest a set of reasons that could justify voting for pro-abortion politicians --- or to argue that no "proportionate reason" can exist in such a case.

Father DiNoia said one obvious proportionate reason would be when, as often occurs, Catholic voters must choose between two candidates who support legalized abortion but to widely differing degrees. In that situation, not to vote at all would seem to go against a Christian's responsibility to participate politically.

But further defining what may or may not be "proportionate reasons" in these cases is extremely difficult, Father DiNoia said. The situation of individual Catholic voters is different, so it's impossible to have a standard list of acceptable reasons, he said.

In the end, then, theology is not able to say categorically in every circumstance when a Catholic voter sins or does not sin. What it can do --- and what the recent memo attempted to do --- is offer principles that are applied to the different situations.

Vatican officials have been reluctant to comment at all on the voting issue, saying it is a complex question that is easily muddled. They say the best thing that could come out of the recent discussion is that Catholics in general think more seriously about their worthiness for Communion.

---CNS