This paper elaborates on the life and publications of Joseph Priestley, the eighteenth-century polymath. The paper outlines his particular place in the European Enlightenment; it stresses the importance of philosophy and worldview in his scientific work on pneumatic chemistry, the composition of air, and his discovery of the process of photosynthesis (or the "restoration of air" as it was called at the time); finally the paper indicates ways in which Priestley's work on photosynthesis can be utilised in the school classroom to advance the understanding of scientific subject matter, to promote an understanding of the nature of scientific procedure and methodology, and finally to evaluate some basic tenets of the European Enlightenment that Priestley so passionately advocated.