Niko Tinbergen's (Zeit. Tier. 20, 1963, 410) paper ‘On aims and methods of ethology’ is appropriately remembered as the paper in which Tinbergen characterized ethology as ‘the biological study of behavior’ and went on to explain that to study behavior biologically is to ask four distinct questions about it: (1) How is it caused physiologically? (2) What is its survival value? (3) How has it evolved? and (4) How does it develop in the individual? Here, we consider Tinbergen's paper in its historical context by looking at it from three different perspectives: (1) a comparison of Tinbergen's formulation of ‘ethology's four questions’ with similar, but different formulations of biology's basic problems offered by Julian Huxley, Konrad Lorenz, and Ernst Mayr; (2) a survey of the roles that the four questions played in Tinbergen's own work over the course of his career; and (3) a consideration of the two explicit goals of Tinbergen's (Zeit. Tier., 20, 1963, 410) paper, namely (a.) to honor Tinbergen's friend and colleague Konrad Lorenz (as part of a Festschrift for Lorenz on the occasion of his sixtieth birthday) and (b.) to provide a sketch of ethology's scope and an evaluation of the ways the field needed to develop in the future. We suggest that just as the work of Tinbergen's Oxford research team revealed how the behavior of gulls reflected compromises worked out in the face of the diverse selective pressures of particular environments, we can identify certain conflicts that arose for Tinbergen in trying to write something that his friend Lorenz would like while also assessing ethology's current state and future prospects. That said, however, Tinbergen's enduring concern was to do all he could to ensure that ethology thrive as a field and develop a scientific understanding of animal (and human) behavior. For this to happen, he insisted, the four questions of ethology needed to be pursued in a balanced, comprehensive, and integrated fashion.