People often ask the question of whether good works are necessary for salvation. Of course, a great deal depends on how one defines salvation in the question. The Bible’s usage is various. It can mean the forgiveness of sins (Luke 1:77). It can mean the future glorified state (Romans 13:11). Surely, it can mean the entire order of salvation as well. Normally, of course, we refer it to simple conversion, “when we were saved.” Realizing these different aspects of our salvation is important to understanding the place of good works.
The other word that can be defined differently in the equation is the word “necessary.” Necessary can mean more than one thing as well. Is the noise of a cannon necessary to its being fired? Yes, but not as the cause of the firing of the cannon, but as part of the effect. Similarly, the time when something is necessary is important to consider. Is something necessary before something else, or after that something else? So, with his usual care and precision, Turretin helps us to understand just how works are necessary to salvation (17.3.14):
Works can be considered in three ways: either with reference to justification or sanctification or glorification. They are related to justification not antecedently, efficiently and meritoriously, but consequently and declaratively. They are related to sanctification constitutively because they constitute and promote it. They are related to glorification antecedently and ordinatively because they are related to it as the means to the end; yea, as the beginning to the complement because grace is glory begun, as glory is grace consummated.
Are works necessary for salvation? Yes, as long as we understand our terms correctly, and so avoid both legalism and antinomianism. If we identify good works as necessary for justification in a constitutive way or a causative way, we have lapsed into legalism. Rather, good works are related to justification much as the noise of a cannon is related to the shot itself. The noise obviously does not constitute the cannonball flying through the air, nor does the noise cause the cannonball to fly through the air. But the noise is always there accompanying and resulting from the cannonball being fired.
Conversely, if we deny any relation of good works to justification, then we lapse into antinomianism. One simply cannot be truly justified without at the same time having the sanctification process start. We cannot separate justification and sanctification.
One last thing ought to be mentioned here. It is fatal to over-react to one error by lapsing into the other error. We can see this happen in history (Richard Baxter’s neonomianism as an over-reaction to the antinomianism of his day comes to mind). The way to react to the one error is to come back to the straight and narrow central path of the gospel that addresses ALL our needs with regard to sin: its condemning power, its reigning power, and its existing power. Justification answers the condemning power of sin. Sanctification answers the reigning power of sin. Glorification answers the existence of sin. Our good works, empowered by the Holy Spirit are a necessary part of the whole picture, in the way that Turretin explained above.