Bacon saw matter as an entity that creates potential worlds by drawing atoms together, thereby forming compounds. Constantly changing matter, with inter-atomic connections that at first were brief, formed our world; gradually, the connections lasted longer, the world stabilized and we now randomly have certain compounds and not others. Not all things that could have formed did indeed form, and consequently, our world with its biodiversity represents only one of many abilities of matter. Furthermore, even today, many species are transient, unstable units that can become other species (maggots to flies). We should apply this secular theory to the creation of a new biodiversity for our benefit. Man should deliberately transform species into other ones by building new combinations and changing forms. Monsters and hybrids hint at the hidden potential of nature, and their study is, therefore, important. We should create new species through parentless generation and then let them develop sexual generation to reproduce. Bacon thus envisioned man as leading drastic diversions of nature’s biodiversity. He demonstrated this vision by describing a utopian, government-supported research institute, which improves diversity by developing formulas by which materials would be mixed to obtain specific creatures. Harvey considered embryonic development as potential realized into form. The egg of the farmyard hen forms and grows by an innate principle that flows from the female’s entire body into her ovaries as innate heat. Yolk and egg white are matter that, after fertilization, gain form by nourishing the foetus, first the yolk and later the egg white. The cock contributes to fertility by transferring an invisible, immaterial entity to the egg, a divine spirit that conveys fertility. Semen also transfers the male’s hereditary traits, as an idea that the uterus “sees” and transforms into matter. The fertilized egg then forms a worm-like embryo, and accordingly, in the embryonic development of complex animals, the early stages represent simple animals. Beyond matter, which eventually gains form, the fertilized egg also has a soul, defined as the ability to produce offspring of the same species. The Sun, as an instrument of God, also influences fertilization. The male receives generative power from the approaching sun and therefore from God. Blood begins life, and since it is the first to appear, it contains the soul. Form development continues well after hatching, in forming crests, combs, wattles and spurs. Harvey studied mammal generation and embryological development in the king’s deer herd. He observed satellite copulation, namely, non-dominant young males secretly mating with the dominant male’s females. In search of semen and some beginnings of life, he dissected the uteri of mated females daily. Finding nothing, he concluded that no conception occurs immediately after coitus. Seven weeks onwards, however, he found pregnant hinds with embryos in the uteri. He generalized that, in both viviparous and oviparous animals, the foetus does not arise from sperm emitted during coitus. He rejected the involvement of ovaries in fertilization. Harvey presented a new definition of the Egg, as the very first stage of embryonic development (the zygote, in our terms). His Egg was an inanimate lump lacking a defined structure, in which the foetus was already present. Life develops from a lifeless, inanimate lump lacking a definite shape. Any primordium from which a living creature generates is thus an egg, whether in the form of a seed or a worm. Mammals produce something resembling an egg, just as plants produce seeds and trees produce fruits. At first, nothing materializes in the uterus; eventually, the “egg” appears. Scientists discovered mammalian egg cells only two centuries after Harvey. Epigenesis, according to Harvey, refers to developing embryos that attract and use material as it comes in. Formation and growth occur simultaneously, and successional embryonic parts differ in matter and form. An embryo progresses from an unorganized, non-functioning body to an organized, functioning one, gradually growing and forming itself, each stage developing into the next. Epigenesis occurs in (the more perfect) vertebrates, which require well-determined matter for growth. The heart, as an instrument of the soul, directs the successive development of the embryo. Metamorphosis, for Harvey, includes both sudden, profound changes in form (insects) and sudden birth directly from matter by spontaneous generation. All matter for a developing embryo is present from the beginning. Consequently, embryonic matter is homogenous, and not much growth occurs. In these lesser animals, created by chance, species are less constant. An egg is a potentially living primordium, whether perfect in the womb, where it reaches final size when laid (birds), or imperfect as it is released immaturely and continues growing after having been laid (insects). From imperfect eggs, imperfect animals ensue (worm, caterpillar) that change into a chrysalis (pupa), which is the perfect, true egg; from it, the prematurely hatched embryo is reborn as an adult. Descartes envisioned the universe as an enormous clockwork, moved by fixed laws, and animals as complex machines that automatically respond to various stimuli, mindlessly following mechanistic rules that move them towards objects to obtain food and generate a way to avoid danger. They have no souls, and accordingly, they are lifeless, self-growing, sometimes self-moving machines devoid of mind, consciousness, sensation, passion, judgement, reason or intelligence. Though acting in ways resembling man, they cannot think. Descartes thus eliminated Life as a category of nature, drawing the line not between living and non-living but between those with a soul (man) versus those without. Man differs from animals in possessing a soul (= mind) that thinks logically and consciously, using senses, images, memories and language to express ideas. The soul, in the pineal gland, is a non-material entity that does not follow the mechanical laws of nature. Descartes’ followers added that animals, having no soul, cannot suffer and therefore do not suffer pain. God created the world along eternal mathematical and mechanical laws that now restrict Him—He cannot break them. Today, God behaves only according to mechanical principles; he has no power to change the course of nature. Consequently, the cosmos is a meaningless entity. During early modern Europe, the detailed study of animal diversity began extending beyond the vertebrates into invertebrate groups. The study of mollusc diversity began with shell classification, the “shell-animals” group including also goose barnacles and tube-dwelling worms. Octopus, squid and terrestrial slugs were, however, included, though without a shell. Shell animals did not include sea slugs, chitons and ammonites, which naturalists regarded as inorganic rock ingredients. Shell classification was global from the start, with each shell represented by a figure, a describing sentence and the locality. Several groups were presented in increasing order of spire height. Terrestrial arthropod and worm diversity is classified by leg and wing morphology, readiness to fly and “nobility”. Socio-political yearnings for a constitutional monarchy trickled into ideas of bee natural history: the hive ruler is an elected monarch; his subjects honour him but keep ancient privileges. He prescribes laws, imposes missions, determines the hive’s timetable and leads the army in battle. He is merciful but intolerant of rebellious bees. Kings form a royal race in which princes are born winged, while commons hatch as worms. Bees generate spontaneously from various carcass parts: kings and princes from brains, common bees from flesh. Drones are weak and impotent. Microscopes first came into biological use in the 1620s, and they served to study the microanatomy of animal organs (capillaries, renal glomeruli, skin microstructure, insect tracheae and leaf pores). They also served in the study of the external morphology of tiny creatures, displaying the complexity of “simple” animals compared to man-made objects. A major contribution was in discovering the vast diversity of unicellular creatures and comprehending their tiny size and huge numbers. Microscopic animals occur in water, soil and inside big animals; some survive years of desiccation in a dried state, “returning to life” when returned to water. By this, temporary pools are colonized, and not by spontaneous generation. Microscopes also enabled the discovery of sperm, which some naturalists then believed to be minute (male and female) organisms. Sperm occur in the uterus after mating, and they contain the potential for forming all the limbs an animal will have at birth. An association of British intellectuals sought to establish a society devoted to the pursuit of experimental knowledge, and Charles II granted royal charters to establish “The Royal Society of London for Improving Natural Knowledge” (1662–1663). These charters espoused many of Bacon’s precepts and objectives, his vision of future science thus becoming a reality. Beyond lectures, discussions and attempts to base knowledge on observations and experiments, the Society also provided a continuing international forum for the practice and development of science through sponsorship of the Philosophical Transactions of the Royal Society (1665). By these means, scientific communication became more dynamic. The Transactions developed a new scientific outlook: articles were to contain no high speculations and no moral lessons; discussions were to be pragmatic interpretations of the results. Through the new science emerging from the Transactions, the study of nature gradually became secular. Transactions also established principles of scientific priority and peer review. The editor became an arbiter, with authority to discredit observations. The Royal Society of London also actively approached scientists to study and publish on specific matters. Several early modern naturalists believed in spontaneous generation. Inferior beings arise from rotting matter by seminal entities that drop from dying plants or animals. Traces of a Force of Life remain in carcasses and generate new living creatures, similar but inferior to the original animal. Animal faeces generate insects, which resemble the animal in whose excrement they were born. Bees are born from cattle manure, and their head resembles that of a cow; stag beetles are born from stag manure, and they resemble a stag’s horns. Animal diversity also consists of many strange hybrids, which develop into dragons. Eventually, careful observations of mosquito life cycles led to doubts about spontaneous generation, and careful experiments found that rotting meat does not generate maggots. There is, thus, no spontaneous generation. Consequently, creatures of one species do not transform into another species—the species is a stable, unchanging entity. Paradoxically, naturalists also believed that insects are born from plant galls and that the production of worms and winged animals may be the primary purpose of a plant, fruit production being only secondary. In all spontaneous generations, however, life arises only from matter that was once alive; it never arises from inorganic matter. Swammerdam opposed Harvey’s theory of the pupa being a second egg. He believed that insects develop gradually, like vertebrates; being as complex as higher organisms, they reflect nature’s unity. The “nymph” is a life stage in which insects have reached adult dimensions. Insects vary in the timing at which they reach it, and this is the basis of their diversity. Four “orders” correspond to different developmental life histories: Spontaneous generation is blasphemy, as it implies that part of nature exempts itself from God’s law and order. His laws of nature are immutable, apply throughout the Creation, and there are no chance events. During the sixteenth century, naturalists debated the essence of fossils. Some claimed that so-called fossil shells are not real seashells but inorganic minerals, growing inside the Earth under the inspiration of mystic powers. Steno found that modern shark teeth resemble fossil ones, and he claimed that rock, once liquid, had solidified around these solid ancient shark teeth. Furthermore, heavy particles sink before fine silt, and similarly, in fossil-bearing deposits in nature, big particles occur below fine ones, suggesting that water had laid them. This explains why fossils in rocks are of aquatic, not terrestrial, creatures. Steno further argued that lower layers are older than higher ones, and so are their fossils. Seashells reached mountaintops by water rising to cover land or by land sinking beneath water. The Earth’s crust, an archive of its ancient history, presents evidence that the world had undergone drastic changes. Steno’s theories were not well received, both for personal animosity and because they were not relevant to ammonites, which do not resemble shells of any living creature. On religious grounds, naturalists rejected the possibility that ammonites represent extinct animals. Ray formulated a reproductive definition of a species, as opposed to definitions of essence. Classifying bird diversity by habitat, feeding mode and morphology, his resulting groups resemble many avian families that we accept today. Aware of natural history, he described anti-predator distraction displays and injury feigning. Ray rejected Epicurus’ theory of randomly colliding atoms as unable to explain the perfect structure of plants, animals and man. He also rejected Descartes’ theory of the mechanics of matter in motion as explaining everything in nature—it does not explain plant and animal diversity, nor why one species cannot form from another. Descartes’ claim that animals lack a soul is also wrong; animals possess rational thinking. God’s will to sustain each species is what rules the world, not mechanical laws. God created Earth as a planet intended just for Man, with the endless diversity of plant and animal species created specifically for his benefit, whether today or in the future. The perfect design of man and animal is evidence of God’s wisdom. This argument, of God’s intended design for a specific purpose, stems from the claim that all phenomena fulfil specific purposes and that an all-knowing entity, God, creates each phenomenon.