Recent research literature in science education, science curriculum documents, and science methods texts have been highly influenced by constructivist views of how students learn science. But the widespread and often uncritical acceptance of constructivism in science education does not reflect the heated debate between constructivists and "realist" science educators over its underlying philosophy, and the curricular and pedagogical implications of constructivism. This paper aims to show that Bernard Lonergan's theory of cognition can inform this debate by (a) suggesting ways to see the merit in the views of constructivists and realists and bridge the gap between them, (b) illustrating how Lonergan's thought can be brought to bear on science curriculum documents and teaching-learning resources for science teachers. Lonergan's Theory of Cognition suggests that human knowing is not a single operation, but a dynamic and integral whole whose parts are sensory experience, understanding, and judging.