Georgetown political philosopher Jason Brennan, author of The Ethics of Voting, has an excellent post refuting the oft-heard mantra that “if you don’t vote, you have no right to complain.” As Jason points out, this argument fails to consider the extremely low likelihood that your vote will actually have an effect on government policy:

The most obvious explanation is that if you don’t vote, you didn’t do something that could influence government in the way you want it to go. You didn’t put in even minimal effort into making a change…..
But voting isn’t like that! The problem is that individual votes don’t make any difference. On the most optimistic assessment of the efficacy of individual votes, votes in, say, the US presidential election can have as high as a 1 in 10 million chance of breaking a tie, but only if you vote in a swing state and vote for one of the two major candidates. Otherwise, the chances of breaking a tie or having any impact are vanishingly small….
[defenders of the argument that if you don’t vote, you have no right to complain] are really saying something like this:
I ran into someone this morning who complained about how poor he is. I told him, “If you’re not playing the lottery everyday, you forfeit your right to complain about being poor.” The problem with poor people is that they don’t buy enough Powerball tickets.

As Brennan explains in his book, sometimes abstaining from voting is not only morally acceptable, but actually morally praiseworthy. One example is when you lack sufficient knowledge of the issues to vote in a minimally informed way, and don’t have the ability or the time to increase your knowledge at least to the point where you are better informed than the average voter. The problem of political ignorance is a very difficult one that no individual citizen can be expected to fix on their own. But they at least should not be stigmatized for abstaining in situations where their participation is likely to make the situation even worse.

UPDATE: I accidentally failed to include a link to Brennan’s post. I apologize for that mistake, which has now been fixed.

UPDATE #2: An additional possible argument for Brennan’s position is that, in some cases, all of the candidates with a realistic chance of winning support policies that are highly unethical or even evil. Voting for them might be considered “complicity with evil” and therefore immoral from the standpoint of several widely accepted versions of ethical theory. I don’t agree with this position myself. In my view, if you pick Candidate A over Candidate B because the former is the lesser evil, without actually condoning A’s evil policies, your actions are not wrong, and you do not become somehow responsible for A’s misdeeds while in office. But the issue is not an easy one, and deserves much more consideration than I can give it here. At the very least, a citizen who chooses not to vote based on such considerations should not be stigmatized as somehow immoral, and certainly has every right to continue to complain about harmful and unjust government policies.