I am unable to make sense of the highlighted sentence in the attached picture, especially the phrase, "leading note" if it's really used as a phrase. Unfortunately, the context doesn't help much as the former and the latter, both are cited sentences.
Robert Boyle exemplifies in most interesting fashion all the leading intellectual currents of his day ; every important or prevalent interest and belief occupied some place in his thinking and the conglomeration was harmonized with considerable success around the foci of his two most dominant enthusiasms, experimental science and religion. Boyle defines philosophy as "a comprehension of all those truths or doctrines, which the natural reason of man, freed from prejudices and partiality, and assisted by learning, attention, exercise,xperiments, etc., can manifestly make out, or by necessary consequence deduce from clear and certain principles. His conception of the leading note of the scientific current of which he formed a part appears at the end of an attack on the highly dogmatic and metaphysical character of the scholastic philosophy. “ Our great Verulam attempted with more skill and industry (and not without some indignation) to restore the more modest and useful way practised by the ancients, of inquiry into particular bodies without hastening to make systems, into the request it formerly had ; wherein the admirable industry of two of our London physicians, Gilbert and Harvey, had not a little assisted him. And I need not tell you that since him Descartes, Gassendi, and others, having taken in the application of geometrical theorems for the explanation of physical problems ; he and they, and other restorers of natural philosophy, have brought the experimental and mathematical way of inquiry into nature, into at least as high and growing an esteem, as it ever possessed when it was most in vogue among the naturalists that preceded Aristotle.
"The metaphysical foundations of modern physical science" E.A. Burtt · 1925