The main question this chapter asks and attempts to answer is: What is the principal difference between animal life and human spirit, as Hegel construes it at the end of his Philosophy of Nature? More specifically, in what way are non-human animal organisms “inadequate” or “imperfect” and in what way, correspondingly, are human beings the “perfect” animal? Answering this question requires getting clear on the different ways in which non-human and human animals bear their respective natures, the connection between reproduction and the manner in which non-human animals relate to their genus, and the role of biological death within that process of reproduction. To the extent that Hegel commentators have dealt with the relation between animal life and human spirit, they have been predominantly concerned in recent years with Hegel’s Anthropology. The end of the Philosophy of Nature has, by contrast, been relatively neglected. On the occasions when it has been discussed, the latter text has tended to be the object of passing paraphrase rather than the focus of an attempt at philosophical comprehension. This chapter contributes to remedying this scholarly situation.

Here, I ask the question: how many planets are there with life in the Milky Way? This question has many variants. We can ask about simple microbial life. Alternatively, we may ask about more complex life – for example multicellular animals and plants. Then again, we may ask specifically about intelligent life. An approach that can be used for all of these variants is the one pioneered by the American astronomer Frank Drake. In this chapter, I use the Drake equation to estimate the number of microbial worlds and the number of worlds with animals. (In a later chapter I use the same approach to estimate the number of worlds with intelligent life.) When Drake first devised his equation, we were hard put to come up with meaningful numerical values for any of its parameters. Now we have reasonably good values for at least some of them. Hence our estimates are better than before. However, there are still wide errors, so I investigate the effects of these errors on our estimates. Bearing them in mind, I only attempt estimates to the nearest order of magnitude. These estimates are: 1 billion planets with microbial life; and 10 million planets with animal life.