has to be ‘indifferent to human preoccupations’ is a misconception associated with the Principle of Mediocrity.
Any assumption that the world is inexplicable can lead only to extremely bad explanations. For an inexplicable world is indistinguishable from one ‘tricked out with capricious ad hoc magic’: by definition, no hypothesis about the world outside the bubble of explicability can be a better explanation than that Zeus rules there – or practically any myth or fantasy one likes.
Moreover, since the outside of the bubble affects our explanations of the inside (or else we may as well do without it), the inside is not really explicable either. It seems so only if we carefully refrain from asking certain questions. This bears an uncanny resemblance to the intellectual landscape before the Enlightenment, with its distinction between Earth and heaven. It is a paradox inherent in the Principle of Mediocrity: contrary to its motivation, here it is forcing us back to an archaic, anthropocentric, pre-scientific conception of the world.
At root, the Principle of Mediocrity and the Spaceship Earth metaphor overlap in a claim about reach: they both claim that the reach of the distinctively human way of being – that is to say, the way of problem-solving, knowledge-creating and adapting the world around us – is bounded. And they argue that its bounds cannot be very far beyond what it has already reached. Trying to go beyond that range must lead to failure and catastrophe respectively.
Both ideas also rely on essentially the same argument, namely that if there were no such limit, there would be no explanation for the continued effectiveness of the adaptations of the human brain beyond the conditions under which they evolved. Why should one adaptation out of the trillions that have ever existed on Earth have unlimited reach, when all others reach only inside the tiny, insignificant, untypical biosphere? Fair enough: all reach has an explanation. But what if there is an explanation, and what if it has nothing to do with evolution or the biosphere?
Imagine that a flock of birds from a species that evolved on one island happens to fly to another. Their wings and eyes still work. That is an example of the reach of those adaptations. It has an explanation, the essence of which is that wings and eyes exploit universal laws of physics (of aerodynamics and optics respectively). They exploit those laws only imperfectly; but the atmospheric and lighting conditions on the two islands are sufficiently similar, by the criteria defined by those laws, for the same adaptations to work on both.
Thus the birds may well be able to fly to an island many kilometres away horizontally, but if they were transported only a few kilometres upwards their wings would stop working because the density of the air would be too low. Their implicit knowledge about how to fly fails at high altitude. A little further up, their eyes and other organs would stop working. The design of these too does not have that much reach: all vertebrate eyes are filled with liquid water, but water freezes at stratospheric temperatures and boils in the vacuum of space. Less dramatically, the birds might also die if they merely had no good night vision and they reached an island where the only suitable prey organisms were nocturnal. For the same reason, biological adaptations also have limited reach in regard to changes in their home environment – which can and do cause extinctions.
If those birds’ adaptations do have enough reach to make the species viable on the new island, they will set up a colony there. In subsequent generations, mutants slightly better adapted to the new island will end up having slightly more offspring on average, so evolution will adapt the population more accurately to contain the knowledge needed to make a living there. The ancestor species of humans colonized new habitats and embarked on new lifestyles in exactly that way. But by the time our species had evolved, our fully human ancestors were achieving much the same thing thousands of times faster, by evolving their cultural knowledge instead. Because they did not yet know how to do science, their knowledge was only a little less parochial than biological knowledge. It consisted of rules of thumb. And so progress, though rapid compared to biological evolution, was sluggish compared to what the Enlightenment has accustomed us to.
Since the Enlightenment, technological progress has depended specifically on the creation of explanatory knowledge. People had dreamed for millennia of flying to the moon, but