What you are apparently failing to realize is that what you are calling conscience simply points you towards Scripture. It doesn't replace it or supersede it as the authority.
Quibbling over terminology.
What governs me from moment to moment? Feelings of certainty - they determine when, if, and how much I read Scripture, they determine whether I even accept that book, and determine whether or not I will feel obligated to obey the dictates of that book.
This is in direct rebuttal of Sola Scriptura defined as: "Scripture is the only final rule of faith and practice."
And if somehow conscience were to replace Scripture, what would it tell every person? About the creating of mankind? About Christ's resurrection from the dead? And a thousand other facts that form our faith as Christians?
So if there were no Bible, it would be impossible to learn these things? Thus in order to know, for example, the facts of Genesis, one NEEDs a Bible? That's odd, because Moses didn't have a Bible when he learned such things. He learned them from direct revelation.
Secondly, who is asking to replace Scripture? What I want is reliably interpret it. When the Third Person enlightens me, I call it direct revelation. After all, when I open the book to read it, there are only two plausible frameworks of enlightenment:
(1) Exegesis-dominant. In this framework, I'm supposed to examine grammar, context, and history, hoping to produce a chain of deductive reasoning culminating in correct conclusions. In this framework, role of the Third Person in enlightenment would be to improve my analytic skills, making me a better scholar, essentially raising my IQ.
(2) Direct revelation. In this framework, I don't deductively infer conclusions. Rather HE
tells me the meaning of the verses, and I accept HIS conclusions based on the perceived authority of the voice, i.e., do I feel certain that this is God speaking and that I heard Him correctly.
Now, which of these two frameworks represents the primary model of divine illumination as God intended it? Again, the two choices are:
(1) Scholarship.
(2) Direct revelation.
Note that, if #1 is correct, scholars would surpassingly unravel all the mysteries of Scripture, leaving the prophets in the dust, and in comparative darkness. But it isn't that a reversal of the facts? Jesus put it this way:
"At that time Jesus said, “I praise you, Father, Lord of heaven and earth, because you have hidden these things from the wise and learned, and
revealed them to little children" (Mat 11:25)
Interesting. Seems like the scholar is totally out of luck compared to those who abound in direct revelation.