Lonergan, like Euclid, Newton, and Mendeleyev, moved through his field of inquiry to the level of system.
(Given the failure to implement the basic expansion,) the systematic requirement of a rate of losses will result in a series of contractions and liquidations. … [CWL 15, 155]
… a science emerges when thinking in a given field moves to the level of system. Prior to Euclid there were many geometrical theorems that had been established. The most notable example is Pythagoras’ theorem on the hypotenuse of the right-angled triangle, which occurs at the end of book 1 of Euclid’s Elements. Euclid’s achievement was to bring together all these scattered theorems by setting up a unitary basis that would handle all of them and a great number of others as well. … Similarly, mechanics became a system with Newton. Prior to Newton, Galileo’s law of the free fall and Kepler’s three laws of planetary motion were known. But these were isolated laws. Galileo’s prescription was that the system was to be a geometry’; so there was something functioning as a system. But the system really emerged with Newton. This is what gave Newton his tremendous influence upon the enlightenment. He laid down a set of basic, definitions, and axioms, and proceeded to demonstrate and conclude from general principles and laws that had been established empirically by his predecessors. Mechanics became a science in the full sense at that point where it became an organized system. … Again, a great deal of chemistry was known prior to Mendeleev. But his discovery of the periodic table selected a set of basic chemical elements and selected them in such a way that further additions could be made to the basic elements. Since that time chemistry has been one single organized subject with a basic set of elements accounting for incredibly vast numbers of compounds. In other words, there is a point in the history of any science when it comes of age, when it has a determinate systematic structure to which corresponds a determinate field. [CWL 14, Method, 1971, 241-42]