Ernst Haeckel

The soul is nothing but the sum of the functions of the brain, and therefore subject to the same laws as all other natural phenomena, including death and decay, and there is no evidence for its immortality or any existence beyond the physical body.

The whole of nature is a single, living, indivisible unity, governed by eternal, immutable laws, and there is no room for supernatural intervention or divine creation, but rather a continuous process of evolution and change.

The law of recapitulation is the most important general law of organic development, and provides the key to understanding the history of life on Earth, from the simplest single-celled organisms to the most complex multicellular forms, including humans, and their evolutionary relationships.

The cell is the true elementary organism, the fundamental form of all living beings, and the starting point for all organic development, from the fertilization of the egg to the formation of the complete organism, and therefore the basis for all biological research and understanding of life.

The human being is only a highly developed mammal, and in no way a special creation, but rather a product of the same natural laws that govern all other organisms, and therefore subject to the same processes of evolution and adaptation, including the development of intelligence and consciousness, and the formation of societies.

Monism is the rational connection of all phenomena in a single, all-encompassing world-view, which recognizes no supernatural forces or beings, and therefore provides a scientific basis for understanding the universe and our place within it, without recourse to religious dogma or anthropocentric biases.

My dear father, I am now a doctor of medicine, and I feel as if I have been reborn. The world lies open before me, and I am eager to conquer it.

The sea is my greatest teacher. It reveals to me the secrets of life and the wonders of creation.

Darwin's theory of evolution is a revelation! It is the key to understanding the diversity of life on Earth.

My work on radiolarians is progressing well. These tiny creatures are masterpieces of natural architecture.

I long for the day when I can dedicate myself entirely to science, free from the constraints of academic life.

The beauty of nature is an inexhaustible source of inspiration for me. I strive to capture its essence in my drawings.

My 'General Morphology' is a bold attempt to synthesize all biological knowledge into a coherent system. It will be a landmark work.

The struggle for existence is a fundamental law of nature. It drives evolution and shapes the forms of life.

I am convinced that all life originated from a single common ancestor. This is the monistic view of the world.

My travels to the tropics have opened my eyes to an astonishing diversity of life. The coral reefs are a true paradise.

The human embryo recapitulates the evolutionary history of its species. This is the biogenetic law.

I am often misunderstood and attacked for my views, but I will not waver in my pursuit of truth.

Art and science are not separate realms; they are two sides of the same coin, both seeking to understand and represent the world.

The 'Riddle of the Universe' is my attempt to provide a comprehensive worldview based on scientific principles.