The short answer is no.
Now for the long answer. And just so you know, I may stick on some clarifications or points that don’t seem all that significant to everyone, but I think there are a lot of places to get confused on this question.
There are multiple questions to consider. The first question regards the participation in evil. Clearly Peter already recognized this issue when he wrote that “publicly funding a direct (and direct is an important word in this) action such as abortion seems to put citizens in a more morally culpable role.” He is right to say that “direct” is an important word here, but it is unclear what this term “direct” means in this case. He uses the phrase “direct action,” which, as far I can tell, would normally refer to the activity of the abortionist. Since, however, the abortionist already directly kills the fetus, I do not think we can make that action any more direct. I am pretty sure you could rephrase his statement as “the government uses taxpayer’s money to support abortion directly.”
Now hang on for the ride as I change the terms some more. Usually when a Catholic attempts to engage in a higher level of ethics or moral theology, he begins using the term “direct” in a particular way, namely, in reference to the principle of double effect, in which one must distinguish between direct and indirect effects. If that were the crucial point in this question, then I think our paying taxes would have an indirect effect. But the principle of double effect is not the crucial point. Directness in this case has to do with immediacy or proximity. What we have here is the question regarding the proximate versus the remote participation/cooperation with evil.
The first distinction we need to make when we consider the cooperation with evil is whether the cooperation is material or formal. Material cooperation is basically the being connected with or related to some aspect of the evil by one of our own actions. (E.g. In Nazi Germany, wicked doctors performed heinous experiments upon some of the prisoners. One of the experiments involved freezing human beings until they died in order to determine in what temperatures the human body could sustain life. That’s pretty messed up. If a researcher were to use the data collected by the Nazis to create a gear that would allow an human being to stay alive in such conditions, say for scientific research in Antarctica, that is a material cooperation. It’s uncomfortable, but I don’t think it would be intrinsically evil.) The second aspect of cooperation with evil is formal cooperation. Basically, the question here is about intention. What is the intent of the cooperation with evil? (For the researcher, he would have formal cooperation if he saw himself as carrying out the activity of the Nazi doctors, or some such thing.) A formal cooperation with evil is impermissible.
I think most if not all people that are part of this blog do not intend to aid the abortion of human beings by paying their taxes, so I do not think there is a formal cooperation. At this point, we must determine when a material cooperation with evil is permissible or impermissible. This is were remoteness and proximity come into play. When one’s cooperation directly produces the evil effect, it is proximate/immediate/direct. When one’s cooperation indirectly produces the evil effect, it is remote/mediate/indirect. There is, however, a sort of spectrum of cooperation from being completely proximate and immediate to being utterly remote and mediate. (E.g. In Lost, when the boy Ecko kills the person, helping the drug lords instill fear into the townspeople, he is cooperating in evil in a completely proximate and immediate way. On the other hand, knowing that the Dallas Cowboys franchise supports Planned Parenthood [jeez, who doesn’t?], were a person to go over to a friend’s house, be offered a cup of coffee, agree to have one, receive the cup in Dallas Cowboys mug, and then actually drink from the Dallas Cowboys mug, that’s about as remote/mediate as it gets.)
It seems to me that paying taxes to the United States goverment, which would in turn fund abortions, would be somewhere in the middle of those two extremes. Though it would be more proximate than our current participation in evil–we already pay taxes to a goverment that actively defends a wicked violation of basic human rights–I do not think that would necessarily make the taxpayer culpable.
There are a few more considerations that we will help us determine the right way of thinking. First off, we are required make our material cooperation as remote as possible. So, all things being equal, we support/engage/utilize whatever is most remotely related to evil. (If the researcher had data from other experiments to find out the temperature a human body can withstand, that would be better to use.) In this case, there are only 2 options: either (a) you pay your taxes and somewhat remotely, somewhat proximately cooperate in a grave evil, or (b) you don’t.
In this case, however, not all other things are equal. We have a grave reason to pay our taxes as well as to minimize our material cooperation with evil. We must pay our taxes because of both the natural law–“Man is a political animal”–and divine command–“Give unto Caesar that which is Caesar’s.” This is not like going to a coffee shop that supports abortion versus going to one that does not. Ethically speaking, you don’t have to drink coffee. But you do have to pay your taxes. And remember, sometimes Caesar was a bad dude.
So no, in this case, I do not think it is makes sense for an individual to evade his taxes into order to avoid the somewhat remote/somewhat proximate participation in the evil of abortion. I do not think the individual is obligated to do so, nor do I think it is permissible in this case.
-Josh
P.S. Thanks, Peter, for the opportunity to word-vomit pedantically all over this blog.