Complex sentence: Among the six systems of Hindu philosophy, early Samkhya and Mimamsa reject the concept of "Ishvara", while later Samkhya, Yoga, Vaisheshika, Vedanta and Nyaya believe in the existence of an Ishvara.
Split into simpler sentences: Among the six systems of Hindu philosophy, Samkhya and Mimamsa do not believe in the concept of "Ishvara". The four other schools, Yoga, Vaisheshika, Vedanta and Nyaya believe in the existence of an Ishvara.