Chapter I: Its Scope and Definition

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_A type of evolution_--Development of an egg 3

_Universality of evolution_--Pervades all nature and concerns
all departments of thought--One half of all science--
Illustrated (1) by human body, (2) by solar system, (3) by
society, (4) by earth, (5) by organic kingdom--The term
evolution usually, but not rightly, confined to this last 3

_Definition of evolution_--_I. Progressive change_--Shown in
the animal body, or the _Ontogenic_ series--In the animal
scale, or the _Taxonomic_ series--In the geological, or
_Phylogenic_ series--The three series similar, though not
identical 8

_II. Change according to certain laws_--Three laws of succession
of organic forms 11

(_a_) _Law of differentiation_--Early forms are generalized;
afterwards separated into specialized forms--Illustrated
by fishes, by birds--Whole process of differentiation
illustrated by growth and branching of a tree 11

(_b_) _Law of progress of the whole_--Mistake of confounding
evolution with upward progress--How far true, and how far
false--Illustrated by branching tree--Examples of this
mistake in the popular mind--In the scientific mind 13

(_c_) _Law of cyclical movement_--Shown in geological history--
Age of mollusks, fishes, reptiles, mammals, man--Illustrated
again by a branching tree--Increasing complexity as well as
height--Illustrated by diagram 16

_The above three laws are laws of evolution_--_Differentiation_
--Shown in the development of an egg, the type of evolution 19

_Progress of the whole_--Not progress of all parts--Shown in
the development of an egg 22

_Cyclical movement_--Less fundamental than other two--Shown in
Ontogeny of body, of mind--Increasing complexity--Necessity
of continued advance--Otherwise deterioration--All these
laws shown in progress of society---Differentiation shown--
Progress of the whole but not of all parts shown--Cyclical
movement shown--In social evolution, however, there is
another element, viz., conscious voluntary progress---This
kind of evolution contrasted with the other 22

_III. Change by means of resident forces_--This is the point of
dispute--Sense in which we use term resident forces--Does
not touch question of origin of natural forces 27

_The two views of the origin of organic forms briefly contrasted_
--As to whether natural or supernatural--As to variability,
definite or indefinite--As to change from one species to
another by transmutation or substitution--As to universality
of law of continuity 29