In chapter 1 of his Synopsis Theologiae Christianae, Melchior Leydekker (1642-1721) briefly comments on the means which one should in the pursuit of theology. He lists five (p. 11):
The pious and painstaking reading, meditation, and comparison of Holy Scripture [in the sense of interpreting Scripture by Scripture] (1 Tim. 4:13; 2 Tim. 3:15).
Faithful and effective prayer (Js. 1:5; Ps. 119:18).
Humble reverence and pious practice toward God (Ps. 111:10; Jn. 5:42, 44; 7:17).
The legitimate use of the writings of ecclesiastics.
The study of the oriental languages, true and solid philosophy, history, etc.
Although he doesn’t elaborate, it seems natural to me that by “the writings of ecclesiastics” he would not only include official church documents such as creeds, confessions, and synodical decrees, but also the books which have been deposited in the church by individual theologians throughout its history. By “oriental” languages, no doubt, Leydekker has in mind the biblical languages (including Greek, of course), not only those which we would refer to as “oriental,” such as Hebrew, Aramaic, etc.
Just a few comments on the first four of these points.
Firstly, as Leydekker points out a few pages before, the external principle (principium externum) of all our theology is Holy Scripture, and the internal principle (principium internum) is the grace of the Holy Spirit, “internally teaching, instructing, and certifying the divinity and true sense of Holy Scripture.” Hence the preeminence he gives to Scripture here.
Secondly, regarding prayer, notice his citation of James 1:5: “If any of you lacks wisdom, let him ask God, who gives generously to all without reproach, and it will be given him.” Students of theology should not depend on their unaided reason, but should constantly look to God in prayer to enlighten their minds as they study.
Thirdly, theology is not merely an intellectual (i.e. theoretical) exercise. Reformed Orthodox theologians emphasised the practical nature of theology, and Leydekker is no exception. He says a few pages earlier that “the whole of theology is practical, inasmuch as it refers, directs, and leads every divine truth perceived by the intellect to practice.” After all, the very name of this blog, taken from Petrus van Mastricht, points to this: theology is the doctrine of living unto God through Christ; that is, doctrine (theoretica) is a means to an end, namely living (practica) unto God through Christ.
Finally, regarding the legitimate use of tradition (i.e. reading the ecclesiastics), see these posts from Richard A. Muller and Carl Trueman.