Complex sentence: He seriously and systematically studied western philosophy and culture, witnessing the endeavors of classical positivism, most notably of his contemporary Auguste Comte, to replace materialism and idealism with a third line in philosophy.
Split into simpler sentences: He seriously and systematically studied western philosophy and culture. He witnessed the endeavors of classical positivism, most notably of his contemporary Auguste Comte, to replace materialism and idealism with a third line in philosophy.