Article 2 of The Belgic confesssion asks the question: By what means is God made known unto us, and gives the answer: “We know him by two means: first, by the creation, preservation and government of the universe; which is before our eyes as a most elegant book, wherein all creatures, great and small, are as so many characters leading us to contemplate the invisible things of God, namely, his power and divinity, as the apostle Paul saith (Rom. 1:20). All which things are sufficient to convince men, and leave them without excuse. Secondly, he makes himself more clearly and fully known to us by his holy and divine Word, that is to say, as far as is necessary for us to know in this life, to his glory and our salvation”.
The words “he makes himself more clearly and fully known” means in effect that knowledge obtained by studying creation, is ancillary to knowledge obtained by studying Scripture.
M.J. Erickson (Introducing Christian Doctrine, 2001 p.49) says “This (general revelation, through creation) should be considered a supplement to, not ’n substitute for, special revelation” (through Scripture).