Sentence:  Francis Moyen was, as here described, an interesting character in his way; a sparkling, talented, thoughtless Parisian, full of adventure and, with his beloved violin in his baggage, ever on the wing. Voltaire and Boileau were winning the world in those days. Moyen, like every young man of the period, had read them, could quote them, and would sometimes utter himself in their particular <WSD>sophy</WSD>; half scoffing, and half religious, and half philosophical by turns, a thorough Frenchman, carelessly throwing off his first thoughts whatever they were and whoever was near. 
Meaning of the word marked with <WSD> tags:  Any one of the various fields of study whose names end in (-sophy).