Biology Reference
In-Depth Information
increases. This law can be understood easily without doing com-
plicated calculations.
Let us return to our game of heads or tails. We begin by doing
series of ten tosses. The theoretical frequency of heads or tails is
50%, but in practice we would not obtain that for each series of
ten tosses. In certain cases we may obtain, for example, seven tails
and three heads, which correspond to frequencies of 70% and 30%.
If we then do series of a million tosses, it is in this case impossible
to obtain 700 000 tails and 300 000 heads complying with the ear-
lier frequencies of 70% and 30%. Owing to the law of large num-
bers, the frequencies observed will be very close to 50%. The
number of deviations compared with this theoretical frequency will
even be so low that it can be ignored. When we repeat several
series of a million tosses, the result will then appear constant and
if we only have access to this overall global result without know-
ing the details of the experiment, random tossing for heads or tails,
we may think that the phenomenon is deterministic whereas it is
probabilistic.
We will come back to this crucial problem in the next chapter.
Schrödinger drew very important consequences from this law of
large numbers which have profoundly marked molecular biology.
2.2.3
Probability, accident and contingency
are not synonymous
The word 'accidental' is often used in place of probabilistic. This is
an approximation which leads to misinterpretations. The major con-
tribution of calculating probabilities is to introduce rational control
of events subject to chance and include them in a scientific analysis.
In contrast, the concept of accident is of pre-scientific origin and
using it constitutes regression in reintroducing the irrational.
Philosophers and scientists have, since ancient times, recognised
the difference between deterministic and probabilistic phenomena,
but up to the 17th century the difference between the two was
believed to be qualitative. Only deterministic phenomena were con-
sidered accessible to science, which consisted, in the essentialism
