Are the bodies of living things (bacteria, plant, animals, humans) running like a purely physical machine or are they coupled with some kind of spiritual soul to breathe life into this machine.

Our scientific research leads us to notice that every detail in cells seems to follow the laws of physics. there is a reason for how organelles, and molecular machines, etc. work.

If the soul somehow helps to make this machine run, then where does the soul's role come into all this and is there any way we can notice its effect?

please back with torah sources or convincing logic.

Note i am not talking about the higher intellectual soul of human beings but rather the lowest level soul, the nefesh, or "life force" common to all living things.

inspired from this comment

The idea of a soul in living things is in many places like shaarei kedusha ch.1 but just wondering how far down the soul operates. Does it reach the level of the physical?

  • The classification of plants as "living things" is a fairly recent innovation that occured only with the advent of cellular biology. Prior to that, only animals were named after their present psyches, distinct from lower "lifeforms".
    – Loewian
    Dec 21, 2015 at 22:10
  • @Loewian source?
    – ray
    Dec 22, 2015 at 6:25
  • E.g. the Rambam in Shemoneh Perakim distinguishes (presumably following Aristotle) between tzomeach and chai (growing and alive) as separate categories. The term "biology" was only coined with during the 1800s a time when philosophical materialism rose to dominance. I suppose it is possible that the parallel Ancient Greek materialists also blurred the lines between sentient and non-sentient organisms, but I recall biologists struggling to justify this by saying life=cells, which was only a meaningful obfuscation with the invention of the microscope.
    – Loewian
    Dec 22, 2015 at 14:29
  • According to the Bavli, the meleches shabbos is distinct between killing an animal (chai - netilas neshama /shochet) vs. killing a plant/fungus (tzomeach - tolesh/kotzer).
    – Loewian
    Dec 22, 2015 at 14:42
  • 1
    Pirkei D'Rabi Eliezer (ch.34): "when a tree is chopped down, its cry goes out from one end of the world to the other. But its cry is not heard"
    – ray
    Dec 22, 2015 at 19:27

2 Answers 2


The Rambam describes the nature of the soul and its faculties in Shemoneh Peraqim. There's a fair, not good, but fair scan of the English available online, but the Touger edition is particularly good and fairly inexpensive. It's short enough to not make sense to cite to, especially because the explanation spans all eight of the chapters, but I'll briefly summarize here.

Essentially, the soul is the principle of life and motion in objects. Anything that is not moved by something else, and moves itself, is said to have a soul. The soul is responsible for growth, sensation, movement, and cogitation. A magnet moves, so it has a soul to account for the movement. A plant grows and moves itself however limitedly, so it has a soul to account for it. Souls are hierarchically arranged based on ability. Minerals are lower than plants, which are lower than animals. Humans top the hierarchy on the basis of our ability to internalize universal truths which are not dependent on bodies for their truth. It is on the basis of this education that human souls are immortal.

The logic behind this is based in hylomorphism, that everything has matter and form. The Rambam states that the soul is the form of the body, and the body is the matter. This is not dualism as a being is made of matter and form. There are not two distinct, accidentally related substances like in many Christian philosophies. By analogy, a computer has a physical substance made of matter, but it also has a program which, while represented physically, is something self moving and able to be cognized. The activities of the computer cannot be adequately explained by the matter alone without addressing the logic of the program. In that way, the computer has primitive soul.

  • interesting. so the soul creates new order whereas a machine always loses order. but how does it work? inside cells all we see is machines. everything seems to follow the laws of physics
    – ray
    Dec 22, 2015 at 18:39
  • The laws of physics are non-deterministic. There are multiple ways things can play out and still be in conformance to those laws. Since we're discussing the Rambam: Aristotle taught as much, believing that all motion begins with an intellect imparting impetus to an object. Therefore intellects intervene, and will is manifest in the universe. There was no room for this kind of thing in Newtonian physics, where the universe was seen as one big clockworks. But Quantum Mechanics and the Uncertainty Principle, are back to promoting a non-deterministic view of how the world runs. Dec 22, 2015 at 20:33
  • 1
    @MichaBerger but quantum mechanics is also clockwork in the sense that there are definite probabilities of events occurring. so the events follow the probabilities. if there were an intelligence there manipulating, it would be noticeable in its going outside the bounds of the expected probabilities
    – ray
    Dec 22, 2015 at 20:52
  • @ray doesn't psychology function on the basis that people are probabilistic too? If you define free will negatively as no other object but the actor necessitates an action, both particles and people have free will, despite being probabilistic. This is how i read rashi on the creation of fruit trees. From a virtue ethic perspective, which is the one found in the eight chapters, one becomes righteous by habituating themselves to choosing wisely, thus increasing their probability of being righteous.
    – ShamanSTK
    Dec 22, 2015 at 22:14
  • I didn't mean I would base my faith on QM being true. Rather, the rishonim discuss the topic in the language of their era. So, they talk Aristotelian metaphysics (or Platonic, or Aristotelian Neo-Platonic, well, you get the idea) and physics. If we want to make sense of what they said in comparison to how /we/ view the world, we need to find how today's physics would frame these ideas. The truth is, QM's deterministic evolution of probability curves has enough room to explain how the same physics doesn't force order or inorder, function or uselessness. Newton's physics made the job harder. Dec 23, 2015 at 1:13

In the Talmud (Sanhedrin 91b) we find:

Antoninus said to Rebbe At what point is the soul given to a human? Is it from the moment of decree [that such a child will exist], or from the moment of formation? He responded: "from the moment of formation." He replied, "is it possible that a piece of meat can last for three days without salt, and yet not become rotten? Rather it must be from the moment of decree." Rebbe said: "This thing that I learned from Antoninus, and there is a supporting verse: [Job 10] Your Providence has guarded my soul."

Within these words we find the purpose and function of the soul. It guards the physical system of which it is attached. We find similarly in Chullin 93b where a body part, although not in operation, is considered to have life to the extent that it doesn't rot.

The physical biological systems are obviously built to do their job. If it wouldn't work it would be a futile, complex design. But indeed, the physical design is necessary and responsible for the success of the organism. However, the more complex something is the more delicate it is. We know all to well how delicate the human being is, for example. This is where the outside influence comes in. The soul is a field, or a bias, nudging things to continue and head in the right direction. We find this expressed in the Medrash Bereishis Rabbah (10:6)

Rebbi Simon taught: There isn't a blade of grass which doesn't have a Mazal (angel) in the heaven hitting it and commanding it, "Grow!" As it says in Iyov, "Knowest thou the ordinances of the heavens? Canst thou establish the dominion thereof in the earth?"

In Etz Chaim of Sifrei Arizal it attributes some form of soul even to inanimate objects. This further points to fact that it is not about making it work.

The idea behind all this is that although God created a closed-system universe (for the most part), He still left it open to influence from above. Randomness is a part of the fabric of the universe. I recall hearing in the name of the Vilna Gaon that God kept weather out of the hands of predictable laws of nanture, and left that in His control. The physical world is not cut off completely but it is surely its own domain. This ratio of physical to spiritual is found in other scenarios as well. The human is mostly desire-driven, but governed by thought, controlled by the conscious self.

  • Interesting about the weather. That interpretation of Ta'anis 2a ("אמר ר' יוחנן ג' מפתחות בידו של הקב"ה שלא נמסרו ביד שליח... מפתח של גשמים דכתיב יפתח ה' לך את אוצרו הטוב את השמים לתת מטר ארצך בעתו") is also found in this article.
    – Fred
    Dec 23, 2015 at 9:52
  • what do you mean by keeping it moving? if everything follows the laws of physics then there is no need for something to keep it moving. so there is no noticeable difference between a machine and a living thing? btw, the soul in animates is just to keep the thing in existence from nothing. that's how i understood it
    – ray
    Dec 23, 2015 at 11:37

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