Perhaps they had consciences, but without the doctrine of the church available, their consciences must have weak, sickly things hardly meriting consideration.  Paul was probably watering down his true views to appeal to the masses, since that was his job, but then perhaps Paul, who also lacked the guidance of the traditions and dogmas of the church, also had a limited conscience capacity due to the lack of catechism available.  It really does raise the question of when, exactly, the church reached its full fruition as to doctrine, thus enabling men to develop fully their consciences.