This dissertation is on scientific understanding, pragmatic rationality, and values in science. I argue for an 'egalitarian' picture of theoretic values and aims in science. Both anti-realists and realists demand that a good theory be empirically adequate. In my dissertation I focus on one important job for science that often does not care for empirical adequacy -- understanding. I look at some important modes of achieving understanding in science and show that they often have very little to do with empirical adequacy. After looking at understanding got from the 'products' of science viz. theories and models, I focus on understanding in relation to activities and practices. This is centered on Hasok Chang's (2009) work on ontological principles and the intelligibility of epistemic activities. Chang's view is that in order for our (pragmatically chosen) epistemic activities to make sense to us, we cannot deny certain corresponding ontological principles, for if we did, the activities would be rendered unintelligible. Finally I look at Duhem's philosophy of physical theory. I situate Duhem among some of his key historical contemporaries Mach, Pearson, and Poincaré and engage in a comparative analysis of these 20th century historian-scientist-philosophers all of whom are widely perceived as paradigmatic instrumentalists. I then launch into Duhem's philosophy. Duhem believed that the aim of physical theory is to classify experimental laws, and that this classification progressively approaches a natural, underlying classification -- call this latter the thesis of natural classification. First I argue that contrary to the views of many scholars, Duhem was not a structural realist. I contend that Duhem was not concerned with structure as it is generally construed, viz. the mathematical form of equations. Duhem was rather concerned with the classification of laws by theory. Finally, I look at Duhem's rationale behind his idea of natural classification. I situate Duhem in Chang's activity-and- principle scheme and argue that for Duhem, in order for the physicist to make sense of her activity of theorizing, she had to affirm the 'principle' or thesis of natural classification. This way I make the move from (Changian) understanding in science, to (Duhemian) understanding of science