Is There Life Elsewhere in the Universe?

Whether or not you think it's likely that there is life elsewhere in the universe is going to depend, I think, very largely on the philosophy you take toward the question of the origin of life. What I've found in my reading is that origin of life researchers tend to fall into two very broad camps which can be called necessitists and contingentists. Necessitists hold that the origin of life is the inevitable product of physical and chemical laws, and that therefore given the physical and chemical laws that control the universe, it's necessary in a nominological sense that life arise in the universe. A good representative of this philosophy would be Christian de Duve, who was a very prominent origin of life researcher who thought that the cosmos is pregnant with human life; it's embodied in its laws. On the other hand, contingentists say that given the laws of physics and chemistry, it's very likely that life would never have evolved anywhere in the cosmos. Rather, the existence of life depends upon a conspiracy of initial conditions that is so improbable that it's very unlikely to have occurred anywhere else in the observable universe. So I think you can see that the perspective of necessitists and contingentists toward the question of extraterrestrial life will largely depend on which camp you belong to. If you're a necessitist then you're going to be very interested in a very young discipline that's only existed since the 1990s called astrobiology. Astrobiology seeks to discover either traces of life or biological signatures of life in extraterrestrial sources like meteorites, lunar soil samples, samples from Mars, and so forth. So far all of these attempts to find biological signatures have been disappointing. So the necessitist, I think, hasn't been very successful in establishing or supporting his claim that life is necessary. On the other hand, the contingentist will not expect to find these sorts of biological signatures because it's so improbable that it's unlikely to have happened anywhere else in the observable universe. So although necessitism tended to be popular during the 60s and the 70s, I think as a result of the failure to find life on Mars and the discovery that Martian chemistry is hostile to life, necessitists have been hard-pressed to support their view. So the current prevailing philosophy tends to be contingentism – that life is not inevitable, that it's highly unlikely dependent upon this contingent conspiracy of circumstances that happen to exist on the prebiotic Earth, but probably not anywhere else.