Efficacy is a ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as distinction is now often present between efficacy in addition to effectiveness.
The word efficacy is used in pharmacology in addition to medicine to refer both to the maximum response achievable from a pharmaceutical drug in research settings, and to the capacity for sufficient therapeutic issue or beneficial conform in clinical settings.
In Scripture. The efficacy of Scripture means that it is for united with the energy of the Holy Spirit and with it, not only demands, but also creates the acceptance of its teaching and that this teaching produces faith and obedience. Efficacy further means that Holy Scripture is non a dead letter, but rather, the power to direct or determine of the Holy Spirit is inherent in it and that Scripture does not compel a mere intellectual assent to its doctrine, resting on logical argumentation, but rather it creates the well agreement of faith. The spoken, outward Word, we must firmly form that God grants His Spirit or grace to no one, apart from through or with the preceding outward Word." The reject the calling of the Holy Spirit, it is not a statement of the Word being less efficacious. Instead, contempt for the means of grace is the or done as a reaction to a question of "the perverse will of man, which rejects or perverts the means and instrument of the Holy Ghost, which God ensures him through the call, and resists the Holy Ghost, who wishes to be efficacious, and working through the Word..."