We use the noun ‘life’ and the verb ‘live’ (lives, lived, living) in ordinary circumstances quite often. Yet it is perhaps not easy to articulate exactly what life is.
One might observe that life is contingent: different forms of life are contingent upon different things. Various forms of physical life depend on various types of matter and energy: oxygen, hydrogen, carbon, heat, light.
We might inquire about non-physical forms of life. One hears the phrase ‘life of the mind’ - is that a metaphor, or a literal reference? Likewise with ‘social life’?
If we restrict ourselves to biological life, we might compare a dead organism to a living one. One of the differences is motion: dead things move when moved; living things move spontaneously. The motion of a non-living thing is ab alio; the motion of a living thing can be ab se.
Life is not measurable in the manner in which we measure matter or energy: a plant or animal does not lose any mass or weight when it dies. Viewing a single-celled organism through a microscope, we cannot see its life disappear when it dies: all the various parts of it remain, and remain in the spatial relation to one another.
What we can see is motion, and death is often inferred when motion stops - correctly inferred or incorrectly inferred. Motion is an indirect, or mediated, sign of life. Motion can fool us; we may think something is alive because it moves, and we might be wrong in so thinking. We may think something is dead because it does not move, and just as easily be right or wrong.
Life, then, might be something metaphysical. If it is not matter or energy or a combination thereof, and if it is not directly detectable by our five senses, it could be a metaphysical category. We note that it is not even detectable in principle by our five senses.
Whether or not one wishes to commit philosophically to a robust ontology, including a metaphysical entity or substance called ‘life’, one can see the reasons which would persuade a philosopher to make that commitment. We might speak of life “going” when a person dies. What is it that went? Whither did it go?
Although some texts include the phrase “self-sustaining” in attempted definitions of ‘life’, this could be true only in a rather limited sense. Given that life is contingent, it is sustained by the ongoing presence of certain types of energy and matter in its environment.
Although living beings may be capable of spontaneous motion, life itself is not spontaneous. Life does not start itself, but rather is started. It does not end itself, but rather is ended. Even in a case of suicide, life is ended by a means, mediately, not by itself directly.
Carl Christian Erhard Schmid wrote an extensive commentary on Kant’s philosophy, and published it in 1798. Summarizing Kant’s views, he gave a four-point Kantian definition of ‘life’ as follows:
1. In general: a substance’s power to determine out of an inner principle to act
2. Particularly: a finite substance’s power to determine itself toward change
3. A material substance’s power to determine itself toward motion and rest as changes of its condition. Because thought and desire are the only inner activities and principles of change which are known to us, but these are not objects of external senses, nor predicates of material substances, life is not ascribed to the latter
4. A being’s power to act according to the laws of the power of desire, i.e., by means of its representation to become the cause of the reality of the objects of these representations.
In German as in English, the verb ‘change’ has both a transitive and a non-transitive semantic; both are in play here. Schmid’s summary in the original reads:
1. Überhaupt: das Verögen einer Substanz, sich aus einem innern Princip zum Handeln zu bestimmen.
2. Insbesondre: das Verögen einer endlichen Substanz, sich zur Veränderung zu bestimmen.
3. Das Vermögen einer materiellen Substanz, sich zur Bewegung und Ruhe, als Veränderungen ihres Zustandes, selbst zu bestimmen. Da Denken und Begehren die einzigen uns bekannten innern Thätigkeiten und Principien einer Veränderung, diese aber keine Gegenstände der äussern Sinne, noch Prädicate materieller Substanzen sind, so kommt letztern eigentlich kein Leben zu.
4. Das Vermögen eines Wesens, nach Gesetzen des Begehrungsvermögens zu handeln d.h. durch seine Vorstellungen Ursache von der Wirklichkeit der Gegenstände dieser Vorstellungen zu werden.
Schmid’s original spelling has been preserved here. If Schmid’s understanding of Kant is correct - and we have reason to think that it is, because Schmid wrote during Kant’s lifetime and received no objection from Kant - then “life” is the power to cause objects to be real, according to Kant. That is quite a statement!
