This blog is part of a short series setting forth my plans for research in the 2015-2016 academic year. It starts with a brief introduction, but each of the pieces stands alone. In this installment, I give a quick and dirty summary of the history of life-concepts in Western culture (Europe and North America from ~1000 BCE to the present).
Concepts of life are as old as recorded history. They are rarely explicit definitions, but they consistently oppose life and non-life/death, either in exclusive categories or as ends of a continuum. 
Greek and Hebrew conversations set the stage for Western discussion. Homer wants to know what holds the limbs together and what remains after death. Genesis identifies life with the breath of God, which gives form, animal life, human life, and spiritual life. Parmenides, Pythagoras, and Plato associate life with the fundamental harmony that orders the universe, while Democritus, Epicurus, and Lucretius want to disentangle the two so that we are free to dissolve into nothingness at death. Thales and Aristotle are more concerned with reconciling biological and abiological causation and explanation. All of them want to understand why and how life manages to surprise us in ways that non-life does not.
Life concepts in the West came to be dominated by the concept of psyche as interpreted by Plato (through Plotinus) – discrete, substantial eternal units of life – and Aristotle – dynamic processes in material substrates. By the Middle Ages, the life of humans takes on a Platonic air, driven by theologians who want to attach it to will, intellect, and the image of God. Meanwhile, the life of plants and animals takes on an Aristotelian air, driven by a desire to conceive of the cosmos as a unified whole. Curiously, both are called psyche or anima. Aquinas attempts to integrate the two with mixed success.
By the start of the 17th century, Aristotelian ideas of formal and final causes have come to be used in ways increasingly unpalatable to natural philosophers. Descartes and Gassendi usher in a “mechanical philosophy,” eliminating those elements.  As formal and final causes are central to the Aristotelian model of life, plant and animal life lose their meaning and human life shifts definitively to a Platonic frame. Life becomes mysterious in the new worldview, and no consensus can be found on how biological causation relates to general causation. This is fertile ground for epistemological inquiries over the next two centuries as the rules of modern science are set. Kant wants to understand living things, while Goethe, Hegel, and others seek to construct historical narratives. In this period, both Progressive and Romantic approaches develop.
Modern science constructed under the mechanical paradigm may not be able to meaningfully differentiate life and non-life. Kant attempted a pragmatic solution, appealing to a concept of organism – parts moving with a common end. He was aware that such an end constitutes a final cause and was, therefore, not justifiable empirically (Critique of Judgment §64-65). Instead he accepted that they must simply be asserted if we want to understand life. Foucault (The Order of Things) describes a broader epistemological shift at this time, from uncovering inherent meaning to taking on the ideal perspective.
In light of this history, Paley did not invent “Design” arguments for living properties.  Instead, he followed Descartes and later enlightenment thinkers in moving the goal-directedness of living things from intrinsic purpose (Aristotelian final cause) to extrinsic Divine purpose. Gassendi, Kant, Hume and others had rejected attempts to determine such purpose empirically, leaving open the question of whether “science” was allowed to determine them in some other way (a priori necessity a la Descartes or pragmatically a la Kant).
In the 19th and early 20th centuries numerous life concepts arose, each gaining only temporary or local popularity. Life might be made up of living stuff. Lucretius proposed “soul-seeds” and Chardin “spirit-matter.” Ruthorford and Soddy suggest radioactive elements as “metabolons.” Moving up into chemical components (rather than atomic) Abernethy proposes a fluid like electricity while Huxley speaks of “protoplasm.”  The Miller-Urey Experiment (1952) was the most famous in a series of experiments establishing that the same components make up life and non-life.
Alternatively, life could be a question of natural laws, with some life-force driving the biosphere toward a particular end, just as the second law of thermodynamics drives the universe toward heat-death. Concepts of “orthogenesis” or progressive evolution became popular among biologists and economists (e.g., Haeckel and Spencer), but they were never fruitful in terms of predictions and were firmly rejected in biology in the early 20th century. 
In the 20th century, life concepts focused on unique functions of life such as metabolism and reproduction. Like life, they appear intuitively distinct and significant. Like life, we have not found any rigorous definitions that match our intuitions. These approaches have opened up productive avenues of research, they have not as of yet provided us with a dominant concept of life. Theologians, philosophers, and ethicists noted the dangers of operationalizing or reducing life and losing value components.
Most recently, we have begun to explore concepts of feedback loops and integrated systems. Von Neumann pioneered this approach with his concept of “cybernetics” and Sara Walker represents the cutting edge of such research applied to definitions of life. The promise lies in recognizing scalable relational properties of physical systems, rather than compositional or energetic properties. These moves were consonant with the process philosophy of Whitehead as well as expressly relational anthropologies, dating at least from Hegel and appearing as I/Thou in Buber.
The next post will explore various modern questions that hang on our model of life.
[Note 1: Non-life and death are not always equivalent.]
[Note 2: See Margaret Osler, Divine Will and the Mechanical Philosophy.]
[Note 3: William Paley is famous as the originator of modern “intelligent design” argument. You may have heard of a watch found on the ground – arguing that it must have been designed because of how it works – or his book, Natural Theology, or Evidences of the Existence and Attributes of the Deity.]
[Note 4: In fiction, the first drives the plot in Frankenstein, the second in R.U.R (Rossum’s Universal Robots).]
[Note 5: See Micheal Ruse’s book, Monad to Man.)]