[Nature study and happiness in life: Hugo de Vries, Eli Heimans and Jac. P. Thijsse]

This article analyses the backgrounds of Hugo de Vries' stance with regard to the Dutch nature study movement, which rapidly gained momentum in the 1890s. The movement has received little attention from historians until now. A short exposition of its aims and intentions, as envisioned by its main protagonists, Heimans and Thijsse, is provided. It is shown that De Vries' scientific ideas on the improvability of the human species and his liberal social views led him to conclude that both socialism and right-wing 'laisser-faire' ideologies were scientifically unsound. Hereditary theory implied that the human races were genetically stable entities which could not be improved by selection of any kind. The progress of society could only be furthered by placing the emphasis on the individual and its cognitive and social development. According to de Vries, the study of nature provided an excellent means to this end, since it contributed to the individual's personal development as well as to its happiness.