When I’ve heard about James Blish’s A Case of Conscience in the past, it’s usually been in comparison to Mary Doria Russell’s The Sparrow. It’s fairly obvious why — both of them deal with a Jesuit on a first-contact mission to an alien planet that is not quite what it first appears — but beyond that (admittedly thorough) superficial resemblance, these are vastly different books.
For one thing, Blish’s book was written in the 1950s, which has certain consequences. First, it’s short. People who grew up reading novels of this length often bitch about modern novels being bloated and padded, but I’ve more often felt that older, short novels don’t have enough time to develop and consequently feel hurried. Happily, A Case of Conscience is an exception to this rule — it feels precisely as long as it needs to be, and makes The Sparrow feel tediously padded in comparison.
The second effect of having been written long ago is that it’s inevitably dated. I’m not a biologist, but the biology here sounds screwy even to me (”recapitulation” as a serious theory, for instance). Fortunately, this isn’t a novel where the science is front and center, so having some oddly quaint theories tossed into the mix adds period flavor rather than destroying the novel’s core. But what is at the core of the novel is Catholic theology, and as the novel predates Vatican II, its theology is perhaps even quainter than its science.
It’s not so much the obsolete points of doctrine that stand out as unmodern, it’s the entire religious worldview of the Jesuit protagonist. Most sympathetic religious characters in modern fiction (including Russell’s protagonist) have personal religions. They agonize over their own belief and action, they worry about their own salvation, they struggle against their own temptation. But Blish’s Jesuit has a more tangible and outward-facing doctrine: When he needs to make a decision on a government mission, he makes it solely on religious grounds; his beliefs about the aliens are shaped entirely by theology; and in general, he views the very framework of the universe through an obtrusively religious lens. The net effect of this, oddly enough, is to make him feel more plausibly like an inhabitant of a strange future, because he’s not much like the people of today.
A Case of Conscience is certainly not a perfect book — it’s got some plot flaws, its characters jump to plot-appropriate conclusions too quickly, and some of the background is implausible fifty years after it was written — but it’s a very good one, and there’s precious little fifty-year-old SF about which that can be said. This is a classic of the genre that holds up shockingly well today, and deserves to be more widely read than it is.