Ernst Haeckel

Ontogeny recapitulates phylogeny.

The cell is the elementary organism.

Ecology is the study of the economy of nature.

Monism is the rational connection of all phenomena in the universe.

The history of the earth is a history of life.

Man is a vertebrate, a mammal, a primate, and an ape.

The soul is a function of the brain.

Art is the highest expression of nature.

The most beautiful forms are found in the simplest organisms.

The whole of organic nature is a single, continuous chain of development.

There is no absolute boundary between the living and the non-living.

The human embryo is a living document of evolution.

Religion is a product of human imagination.

Science is the only true path to knowledge.

The beauty of nature is inexhaustible.

Every organism is a work of art.

The struggle for existence is the engine of evolution.

The human race is a single species, but with many varieties.

The universe is a single, unified whole.

The laws of nature are immutable.