Of all living organisms in the world, arguably the most complex, enigmatic, and independent, and as a result, interesting—is man. From its physiology to its psychology, the human is one of the most studied yet most misunderstood organism, the most intriguing living thing of which we know. Generally understood to have free will, we can will our own actions, and we are self-conscious, unlike other animals, and we can question ourselves. And as genius inventors, we have even created artificial intelligence, robots, machines, non-living things capable of logical reasoning. It is quite easy, though, to distinguish animals and machines from humans—or is it? During the 17th- and 18th-centuries, it was not uncommon to think of man as a functional, conscious machine, a mere sum of parts.
The first philosopher to elaborate on the idea of organisms as machines was French philosopher René Descartes (1596-1650), who was famous for stating his immortal, “I think, therefore I am.” When it came to living things, Descartes practiced biological reductionism, which meant that he viewed living things not in terms of wholes, but as sums of parts. To illustrate this, think of a computer: As a whole, it is a computer, but we can break it down to its core components, like its keyboard, trackpad, screen, and we can go further, reducing it to smaller parts, like the microprocessor. Similarly, Descartes took man and reduced him to smaller parts. After all, the human body is really just a system of interchangeable parts. We are humans as a whole, but we are made up of numerous body parts, each of which could theoretically be replaced. If we can build a machine with replaceable parts, thought Descartes, what was to distinguish us humans, then, from machines? Another aspect of machines is the fact that they are passive, which is to say that they do not act but react. It is safe to say, for the sake of this argument, that machines have no free will; they cannot act voluntarily. Descartes saw us the same way, reminding us that man is subject to physical laws, over which we have no control, such as gravity and temperature. We may be able to adapt to them, but they cannot be avoided altogether. As such, Descartes concluded that humans were passive and reactive. There was a fundamental difference between humans and animals, whom Descartes designated pejoratively as “brutes,” he conceded. (Apparently, comparing man to a machine was not as degrading, and for that matter dehumanizing, as comparing him to a lowly animal.) Descartes attributed to all living things a will, a drive from which all actions are derived, from which instincts arise. Within all animals, there is some kind of “animal spirit” coursing through their blood in their veins. We say that our thoughts cause our actions; in the same manner, Descartes asserted that these “animal spirits” were the source of action. For this reason, his idea of “will” is different from ours in that it does not cause directly. Accordingly, animals function entirely by involuntary actions, by fulfilling their survival instincts; no room is there in the animal for voluntary contemplation, as its only actions are those which are carried out for the sake of its survival, which themselves are unconscious. Here Descartes provides the distinction between brute and man: the Soul. Being the dualist that he was, Descartes marked a fine line between the physical and mental, body and mind. Man had a soul, unlike animals. The soul was a vital, animating force that made man conscious. The link between mind and body lay in the pineal gland, said Descartes. Endowed with a soul, man was able to take control voluntarily over his animal spirits, thereby allowing him to have free will.
A contemporary of Descartes, the next mechanistic thinker was Englishman Thomas Hobbes (1588-1679). The political philosopher who authored The Leviathan was influenced by Newtonian physics, and this interest in the natural sciences would play a major rule in his view of human nature. Hobbes was a physicalist, meaning he thought only physical bodies exist, and that reality consisted solely thereof. There was no room for God, nor for some kind of “soul,” as Descartes posited—no form of vitalism. Everything, Hobbes confidently said, could be explained by motion, which he defined as “a continual relinquishing of one place and acquiring of another.” Armed with Newtonian mechanics, a physicalist view of reality, and a naturalistic metaphysics based on motion, Hobbes was determined to prove that human nature could be reduced to pure physical motion, and nothing else. The basic drive of organisms was movement, and of that, there were two types: vital and voluntary. Vital movement was unconscious and consisted of necessary living functions—one can see the parallel to Descartes’ animal spirits. Humans need to eat and drink, so they choose vital movement, resulting in the act of eating or drinking, respectively. And remember that the acts of eating and drinking are physical, enacted in terms of motion, namely the picking up of said nourishment and the actual process of ingesting it. Along with vital movement, there is voluntary movement, which is conscious and willed. Voluntary movement is unnecessary to the extent that it is not required for survival. Watching television or playing sports is voluntary because we choose to do it and do not need to do it. This, however, left a large problem for Hobbes, the same one that plagued Descartes, and even neurologists today: How do we account for mental thoughts physically? Hobbes explained thought in terms of motion. When we eat, it is because our voluntary movement tells us to, and our voluntary movement tells us to, because we think it, so thought causes movement, which in turn causes whatever process we thought of. Hobbes was an empiricist, fittingly, when it came to explaining thought processes. He proposed that thoughts are derived from experience. All thoughts are of phenomena we have experienced, so our thoughts are based on perception. The process of thinking is merely a process of internalizing; we experience an outside phenomena, creating a mental image, which itself is not mental, but physical, manifest in motion. All perceptions Hobbes called “phantasms.” Phantasms can be either objects perceived or qualities of an object that are perceived; either way, both are involved. For example, a green ball, while one perception, consists visually of two phantasms: the ball, the object, and the greenness, the quality of the ball. But if thought is perceptual, it meant Hobbes had to come up with an answer to the fact that we can conjure up thoughts out of thin air. To this Hobbes replied that humans have an ability he called “imagination.” Imagination was the “decay” of perception—in other words, a memory. We are able to think of previous perceptions because we can recall them. Keep in mind, again, that all these processes are to be thought of in terms of physical motion. Memory is chronological, but its chain of events can be interrupted, Hobbes suggested, thus accounting for inaccurate memories. However, it seems Hobbes did not account for synthetic a priori truths. In this way, Hobbes managed to reduce man, a complex organism, to a mere object of physical laws, nowise more animate than a robot. He, like Descartes, said man was different from animals because he possessed the ability to create “signs” and “names” symbolic of objects. We call a door a “door” and assign it that value; animals cannot do that. He also grants us two types of knowledge that we can use to our advantage: factual and consequential. The former is the ability to recall facts, and the latter to create causal connections between A and B. Further, Hobbes says man can use logic, which he defined as the ability to add or subtract abstractions. The idea of Man can be added with another abstract concept (Hobbes said “Man” was abstract), like Love, or subtracted from another, like Nature.
Finally, the last and most infamous of the mechanists was the French thinker Julien Offray de La Mettrie (1709-1751). Having studied physiology under the famed physician Herman Boerhaave, La Mettrie would later serve as the physician to Frederick the Great, but between then, his background in medicine would pave the way for his controversial philosophy. La Mettrie was practically a villain in 18th-century France, called everything from an atheist to a determinist to a hedonist to a materialist, the last of which was commonplace and not derogatory. His books were burned publicly and outlawed by the government after they were read, and he was exiled on several occasions. His philosophy was a combination of naturalism, biology, and Cartesian mechanism and resulted in a mechanistic view of man. In his 1745 work Histoire Naturelle de l’Âme, Natural History of the Soul, he dismissed any idea of a soul, rejecting any form of vitalism, stating that there was no animating element in living things. He completely rejected Cartesian dualism, demanding that there was only matter and bodies. His next work was his magnum opus and served as a major tour de force. L’Homme Machine (1748), translated as “Man a Machine,” was La Mettrie’s masterpiece, and in it he wrote that there was no free will. Our actions, as we discussed with Hobbes, are considered to be the result of our thoughts. La Mettrie argued that even our thoughts are not technically our own, seeing as our thoughts are determined first by the condition of our body or health. We are not able to do things we would normally be able to do when we are healthy when we are sick, and vice versa. Depending on the state of our health, we are disposed to certain things, and the state of our health, as we know, is seldom within our control, but left, rather, to other determinants. La Mettrie was also an opponent of Leibniz, who wrote about monads, self-contained entities. In response, he wrote, “They [non-materialists] have spiritualized matter rather than materializing the soul. How can we define a being whose nature is utterly unknown to us?” Thinkers like Leibniz he criticized for advocating a form of vitalism by positing a force of some kind. Likewise, Descartes would have been targeted by this comment and blamed for “spiritualizing matter” because he talked of his animal spirits—a foolish mistake to La Mettrie. Instead, he, Descartes, should have explained these animal spirits physically, as Hobbes did. La Mettrie then wrote Les Animaux plus que Machines (Animals More Than Machines) wherein he created his own way of bypassing vitalism while at the same time advancing a type sentience in animals, humans included. He said that animals were not alive, so to speak, which is to say that they did not possess some kind of living spirit, but they had the ability to feel. La Mettrie in the same book described his own theory of evolution that saw each evolution increase in its desires. Plants had very little needs but were simple organism, and they evolved into animals, which had more needs, and they evolved into humans, who have many needs, whereof many are unnecessary. La Mettrie then wrote that thoughts are physical and cause emotions and bodily sensations within the body, a view similar to Hobbes’. His ethical works consist of Discours sur le Bonheur (1748), Discourse on Happiness, and L’Art de Jouir (1751), The Art of Enjoyment. The first work depicted virtue as a dual development of amour de soi, a love for oneself, and happiness. This is unlike other philosophers, who inverted the equation, equating happiness with virtue, not the other way around. He also wrote that laws were a social necessity. His later work, as can be surmised by the title, was more sensual and detailed a hedonistic ethical theory. La Mettrie identified pleasure as either debauchery (débauche) or enjoyment (volupté). Debauchery, as La Mettrie saw it, was better than enjoyment, for it did no harm, whereas enjoyment does. For this reason, La Mettrie is sometimes said to be a Utilitarian, as he preferred the former to the latter, non-harm to harm.
Looking back at the history of ideas, we cannot help but think some foolish, others wise beyond their years. Nowadays, were someone to ask if we were machines, we would think them crazy: How could we, such complex, thoughtful beings, possibly be mindless A.I.? It is unfair, though, to judge an idea 400 years old, considering we have made considerable advances, both in biology and neurology, that have disproved this notion. This is not to dismiss the idea completely, however, as it is an interesting topic worthy of discussion even today—food for thought, if you will. In fact, how do we know we aren’t machines ourselves, built by some other complex race of intelligent beings? Who knows.
 Stumpf, Socrates to Sartre, p. 220
 Arp, 1001 Ideas that Changed the Way We Think, p. 405
For further reading:
The Blackwell Companion to the Enlightenment by John. W. Yolton (1992)
1001 Ideas that Changed the Way We Think by Robert Arp (2013)
A History of Modern Philosophy Vol. 1 by Harald Høffding (1955)
A Critical History of Western Philosophy by D.J. O’Connor (1964)
The Encyclopedia of Philosophy Vol. 4 by Paul Edwards (1967)
The Story of Civilization Vol. 9 by Will Durant (1965)
Socrates to Sartre by Enoch Samuel Stumpf (1982)