Stephen Jay Gould (1980) has remarked, in explaining the role that contingency has played in evolution and in history, that “contingency is not the same as randomness”. I would add (as he would agree) that it is not the same as necessity either. Thus we have to add a third term to the immemorial philosophical counterposition of chance and necessity – a highly significant middle term.

Contingency arises when several alternative consequences can arise from the present cause, i.e. several alternative subsequent states can arise from the present state of the system. They do not have to be equally probable; the likelihood of their future occurrence will be weighted by those probabilities. The main point is that the next state of the system is not strictly predictable. Since predictability is not the same as determinism (as we know from chaos theory), determinism is not really in question. The choice between the alternatives may be determined by the precise (knife-edge precision) starting position, where infinitesimally adjacent positions may cause divergent outcomes. (Cf. the previous essay on “Symmetry- Breaking”.)

We often perceive “crossroads” or a “parting of the ways” in history; and we see “bifurcations” in the evolution of life forms. It is often a choice of two alternatives, but sometimes more than two. It is a mechanism very similar to (if not identical with) “symmetry breaking”. This mechanism arises from the fact (not initially acknowledged in the theory of causality) that cause-and-effect sequences are not necessarily straight chains; they can be branched, both at the “cause” end and at the “effect” end. Multi- causal events are now well known, e.g. in the causes of war. But contingency, as discussed here, is a case of branching at the “effect” end.

As Gould maintains, life on Earth could have evolved in many alternative directions (several at each of many forking points), most of which would not include humans. And if the tape were rewound and allowed to run again, we would not be here. But it had to go this way, by the anthropic principle, because we are here to discuss it.

There is also another point to note here. The rewinding and re-running of the tape of evolution would most likely not produce the results observed at present, but by means of convergent evolution (where you get a “marsupial wolf’ or a fish bearing live young) it could still produce something essentially like a human, although not in mammal form. A big-brained dinosaur has been suspected to have existed. (Cf. essay “Convergence in Biology” in Section VIII.)

The relationships between necessity, contingency, and chance (randomness) are somewhat like the relationships between “brown music” (varying only one note at a time, as in Brownian motion), 1/f or what I call “beige music” which is most pleasing to our ears in melody, and “white music” which jumps all over the place without rhyme or reason. (Cf. “Music and Life” in Section VI.) I.e. it is neither too monotonous nor too wild, neither catatonic nor hyper-active, but “just right”, most life-like. (Cf. “The Goldilocks Effect” in Section VIII.)

Contingency is the main feature of the historical way of knowledge, whether of biological history or human history. Predictability (necessity) is the main feature of physical sciences. Is it contingency that introduces the arrow of time into history, which is lacking in science (excluding thennodynamics)? Possibly, since we cannot “rewind the tape”, and so we lose time-reversibility.

However, on this day (November 30, 1995), the day of the Quebec referendum, when many in ROC (the rest of Canada) are saying “My Canada includes Quebec”, I want to add “My Earth includes humans” .