As in many classifications, there is no hard and fast boundary between the organic and the inorganic. An organism must be able to reproduce itself and be capable of action to make the most of its environment, but crystals of inorganic substances can do this and nobody would regard these as being alive in the conventional sense. Because there is no hard and fast boundary it scarcely matters where we choose to put it, but it is clearly the case that there is a difference of kind between the inorganic and the living higher organism, at least from the simple cell upwards.
The living higher organism can actively interface with its environment in seeking the raw materials for growth, reproduction and change. This requires a degree of mobility and this in turn requires a complex biochemistry with a specialisation of function that implies cell structure. When the biochemical mechanisms are functioning the organism is alive, but when they cease functioning due to an accumulation of toxins the organism dies. The spark of life is the functioning of the interlocking biochemical machinery of the individual that alone gives a meaning to its biological structure – without this the individual is just a complex collection of uncoordinated chemicals.
Numerous attempts have been made at explaining the emergence of higher life forms from the ‘primeval soup ‘, and some steps have been synthesized . It is recognised that the physical environment of our world must have been radically different in its earlier years, so we do not need to postulate a mechanism that could operate today. We could even move the problem further away by settling for an extraterrestrial mechanism.
The important thing is that some time during or since the Big Bang simple elements combined into chemical compounds of great complexity in which continuous self-sustaining processes could occur because of the basic characteristics of the original building blocks. Many elements are involved, but it all goes back initially to the properties of the hydrogen atom, from which we know the others were derived. The basic building blocks must have properties that enable them in the right conditions to change to other elements and to combine into innumerable inorganic and organic chemicals. The full details of how this comes about are well on the way to being understood. The origin of the basic building blocks is another matter, and this leads us straight back to the intellectual problems of infinity.
Having gone a long way to understand what appears to be a mechanical progression from hydrogen atom to higher life forms, it is necessary to step back and consider why at least the human individual feels himself to be alive in some entirely personal sense, with numerous attributes special to himself.
One very large part of an individual’s attributes are physical. Male or female; old or young; big or small; large or small brain; ugly or beautiful, large glands of one sort or another, or small glands with the same functions – let us not delude ourselves, these physical factors are of paramount importance in delineating our individual egos.