What does one understand by "animal and human behaviour"? In order to understand animal and human behaviour one must first understand what is meant by behaviour. The behaviour or manifestation of a being is a result of its very highest, innermost and vital urge or instinct, namely the instinct of self-preservation. Without this urge the I or innermost self of the living being cannot possibly experience life. The I of the living being is, as explained in my main work "Livets Bog (The Book of Life)", certainly an eternal reality, but this eternal existence would mean nothing whatsoever if it could not be experienced by the I. But in order to be experienced it must appear as mutually contrasting details. And it is by virtue of this principle of contrast that the experience of life takes the form of an evolution from primitive to perfect forms, from mineral to plant, from plant to animal and from animal to human being and so on. The difference between the animal mentality and the human mentality is thus a difference in evolution. The animal mentality is primitive, while the human mentality is further advanced in evolution and manifests, at its highest stage, high-intellectuality.