Complex sentence: By the time of Constantine the Christian church had become an effective instrument of exploitation; but Thomas saw hope in the prophetic protests that had arisen from time to time in Christian history and were now emphasized by the Social Gospel.
Split into simpler sentences: By the time of Constantine the Christian church had become an effective instrument of exploitation. But Thomas saw hope in the prophetic protests that had arisen from time to time in Christian history and were now emphasized by the Social Gospel.