Gillespie asserts the importance of maintaining the truth against the inroads of error. He answers basic questions: What is heresy? How should we respond to heresy?
At the outset, Gillespie stresses the need for stability and firmness in the truth: "Skepticism, fluctuation and wavering, concerning those things which God has revealed to be believed or done by us, is a sin; and to be firm, fixed and established in the faith is a duty commanded."
Next, Gillespie gives a definition of heresy, based upon numerous references in Scripture. He provides a detailed consideration of 1 Cor. 11:19. He states, godly men "are known by this as one of their characters: they hate, avoid, and resist heresies, and earnestly contend for the faith."
Finally, Gillespie mentions several guidelines for evaluating the "new lights" offered by men who attempt to modify or overthrow established doctrine.
George Gillespie (1613-1648) was a Scottish Commissioner to the Westminster Assembly.