Any 21st century high school graduate knows a great deal about animals. An animal is made of organs, which are made of tissues, which are made of cells, which are made of macromolecules, which are made of atoms. An animal has circulating blood (hemolymph for invertebrates) pumped by the heart; it moves by contracting muscles as commanded by nerve impulses coming from the brain. Animals obtain energy by eating and breathing. When animals mate, the male animal's sperm combines with the female animal's egg; the genetic material of the two cells join into one, which provides the information that organizes the developing embryo. Animals are divided into species, which are grouped into higher taxons: genera, families, orders, classes, phyla. All animals are descended from a common Precambrian ancestor; their present diversity is due to evolution as guided by natural selection. None of it was known to humanity from the beginning; all of it was discovered in the last few centuries.
Now, suppose you know none of it because it hasn't yet been discovered, and do not even have the language to describe it. You cannot speak of sperm and eggs containing information or food containing energy because the concepts of information and energy haven't yet been invented. You have never seen spermatozoa because the microscope hasn't yet been invented. You don't understand that inheritance comes in discrete units of genes, which appear in variants - alleles. You have no clue, what the heart, muscles, brain are for, or that blood circulates. You don't have a good notion of species and never thought of evolution. You have never dissected a human corpse. Yet you are one of the greatest geniuses in the history of humanity, and you want to write a treatise on the anatomy, physiology and ethology of animals, including humans. What do you do?
What Aristotle did was, inevitably, to get almost all the theory wrong: the purpose of the brain and the heart, the process of fertilization, the sexes of the bees. Some observations, however, are right: that sponges aren't plants, that whales and dolphins aren't fish, that in a certain species of catfish, the male guards the brood, that the octopus has a breakable penis-tentacle, that the dogfish give birth to live young, which are attached to the womb through a kind of placenta, like mammals. The worst thing is that for almost 2000 years his writings were considered the absolute truth. It was only during the Renaissance that science advanced beyond: Harvey and Malpighi discovered the circulation of blood, Vesalius produced a correct human anatomy based on dissecting many corpses, van Leeuwenhoek and Hooke discovered cells, Linnaeus took a stab at classifying animals. Over the next few centuries, this knowledge was refined and added to by Darwin and Wallace, Watson and Creek, and other biologists. What this book is trying to do, though, rather than condemn Aristotle for being wrong, to look at him on his own terms.