A phisico-theological discourse upon the Divine Being, or first cause of all things, providence of God, general and particular, separate existence of the human soul, certainty of reveal'd religion, fallacy of modern inspiration, and danger of enthusiasm : to which is added An appendix concerning the corruption of humane nature, the force of habits, and the necessity of supernatural aid to the acquest of eternal happiness : with epistolary conferences between the deceased Dr. Anthony Horneck and the author, relating to these subjects : in several letters from a gentleman to his doubting friend