ation and "a body of discoveries about mankind."[11]
In the hierarchy of the sciences, sociology, the last in time, was first
in importance. The order was as follows: mathematics, astronomy,
physics, chemistry, biology including psychology, sociology. This order
represented a progression from the more elementary to the more complex.
It was because history and politics were concerned with the most complex
of natural phenomena that they were the last to achieve what Comte
called the positive character. They did this in sociology.

Many attempts have been made before and since Comte to find a
satisfactory classification of the sciences. The order and relation of
the sciences is still, in fact, one of the cardinal problems of
philosophy. In recent years the notion has gained recognition that the
difference between history and the natural sciences is not one of
degree, but of kind; not of subject-matter merely, but of method. This
difference in method is, however, fundamental. It is a difference not
merely in the interpretation but in the _logical character_ of facts.

Every historical fact, it is pointed out, is concerned with a unique
event. History never repeats itself. If nothing else, the mere
circumstance that every event has a _date_ and _location_ would give
historical facts an individuality that facts of the abstract sciences do
not possess. Because historical facts always are located and dated, and
cannot therefore be repeated, they are not subject to experiment and
verification. On the other hand, a fact not subject to verification is
not a fact for natural science. History, as distinguished from natural
history, deals with individuals, i.e., individual events, persons,
institutions. Natural science is concerned, not with individuals, but
with classes, types, species. All the assertions that are valid for
natural science concern classes. An illustration will make this
distinction clear.

Sometime in October, 1838, Charles Darwin happened to pick up and read
Malthus' book on _Population_. The facts of "the struggle for
existence," so strikingly presented in that now celebrated volume,
suggested an explanation of a problem which had long interested and
puzzled him, namely, the origin of species.

This is a statement of a historical fact, and the point is that it is
not subject to empirical verification. It cannot be stated, in other
words, in the form of a hypothesis, which further observation of other
men of th