This has turned out to be a bit of a weird list, partly I think because I don't have a very strong opinion about quite a lot of big political issues, e.g. economics. Also I don't read enough non-fiction, and what I do read tends to be non-polemical, and in any case I tend to be preoccupied with cultural and social issues rather than strictly political ones.
Practical Ethics, Peter Singer
The moral status of the foetus/unborn child is the central philosophical question in the abortion debate, but it is rare to encounter serious discussion of the issue. Most pro-abortion argument is long on hand-waving about irrelevancies and short on engagement with this central problem – largely, I suspect, because pro-abortion folk know that the premises on which the pro-abortion argument depends lead down some difficult conceptual roads. Singer, by contrast, cuts to the quick. He has a coherent and plausible (though in my view false) idea of which categories of human being have the right to life – and which don’t – and is happy to embrace all the logical outworkings of that idea, most famously perhaps in his argument that since there do not seem to be good reasons to regard birth as a morally significant boundary, young children also lack the right to life. Singer gives the abortion-sceptic a genuine argument to engage with, and is an honest interlocutor.
See also: another book arguing for a liberal position on abortion (and euthanasia) which I think makes a solid and well-argued if ultimately unconvincing case, Ronald Dworkin’s Life’s Dominion.
“A Defence Of Abortion”, Judith Jarvis Thomson
The "violinist" thought experiment proposed by Judith Jarvis Thomson is unlike most arguments for the permissibility of abortion in that it attempts to show that abortion is acceptable even granting the pro-life premises about the moral status of the unborn child. I don’t think she ultimately succeeds, for reasons much too long-winded to go into here, but thoughtful anti-abortionists have to engage with this paper (we should also think about why she's wrong when she denies the rights of the unborn on the grounds that “acorns are not oak trees”).
“Euthypro”, by Plato
In the course of this dialogue Plato raises what has became a widely-quoted challenge to the coherence of conventional Christian ideas about God, the so-called “Euthypro dilemma”: are good things good because God commands them, or does God command them because they are good? Either option raises serious problems for the believer; notably, the first answer appears to make God arbitrary or capricious, while the second appears to situate the source of morality away from God. Personally I am persuaded by Christian responses to the apparent difficulty – and in general have concluded that atheist accounts of morality raise many more problems than Christian ones – but there is still a lot to be gained by thinking through the issues raised in the dialogue.
See also: Stephen Law’s “The Evil God Challenge”, a tricksy and hard-to-answer little paper that has forced Christian philosophers and apologists to be more exact and rigorous about the conclusions they draw about God’s nature from the created world.
The Rights Of Man, Tom Paine
It’s not the most scholarly or systematic expression of Enlightenment political thought, but it’s punchy and readable, fizzing with energy and ideas and a serious challenge to Burke’s Reflections On The Revolution In France and to conservative political thought more generally. For conservatives like me who have serious reservations about some of the many ideas that sail under the banner of “The Enlightenment”, it’s authors like Paine who remind you of the awful injustices and brutalities that gave rise to the fierce reforming zeal of the time, even if we continue to regard his solutions as wrongheaded.
Various works, Bart Ehrman
Ehrman, an ex-Christian, is a well-known “scholarly sceptic” of traditional Christian claims about the early church and the reliability of the New Testament, who has helped to popularise the insights of the “textual criticism” that has so transformed the academy’s attitude to Christianity in the last two centuries. He has argued, inter alia, that we cannot know with any certainty what Jesus said, that Jesus never claimed to be God, that we cannot be sure what the New Testament originally said or what the first Christians believed, and that parts of the New Testament may be forged.
Although many of his conclusions are highly disputable (and disputed), he has made clear the kind of questions that Christian scholars and historians need to answer if they wish to uphold a Christian faith grounded in history and fact.