General revelation is the knowledge of God, as well as the knowledge of right and wrong, that can be obtained through nature. This general revelation of God’s existence and basic morality is known by everyone. First of all, the apostle Paul tells us that the people can obtain knowledge of God in creation.
Knowledge of God, Rom. 1:18-20, “For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, 19 because that which is known about God is evident within them; for God made it evident to them. 20 For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse.”
Paul goes on to tell us that there is a natural order of morality written on the hearts of all people.
Knowledge of Morality, Rom. 2:14-15, “For when Gentiles who do not have the Law do instinctively the things of the Law, these, not having the Law, are a law to themselves, 15 in that they show the work of the Law written in their hearts, their conscience bearing witness, and their thoughts alternately accusing or else defending them.”
This morality, however, is obscured by people's natural sinfulness and the cultures in which they are raised. So, though the basics of proper morality are written on the hearts of everyone, people's different situations, culture, upbringing, etc., obscure proper moral understanding.
The Bible tells us that non-Christians have sufficient knowledge of God as well as knowledge of right and wrong, but that they are suppressing the truth of this knowledge in their own unrighteousness. Therefore, all people are without excuse before God since the Scriptures tell us that the knowledge of God and the knowledge of sufficient moral responsibility can be seen in creation as well as known in the heart.
Special revelation is the revelation of God that is mainly known as the Bible, which is the inspired word. But, special revelation is not limited to the Bible alone. There are many things that Jesus did that are not recorded in the Bible. Most probably there are things the Old Testament prophets and New Testament apostles did and said that were specially revealed from God, but are not recorded in the Bible. Finally, depending on which view of the charismatic gifts you might hold, if the charismatic gifts are still in operation, then a case could be made that such manifestation of the Holy Spirit’s work would also be considered special revelation.
The difference between general and special revelation
General revelation does not provide sufficient information for the gospel message. The gospel, which is the death, burial, and resurrection of Jesus, is found in the Bible. So, where general revelation deals with the existence of God and generic morality, special revelation, the Bible, and the person of Christ, give specifics regarding sin, salvation, heaven, hell, the nature of God, the Trinity, the incarnation, death, the Fall, redemption, etc.
Because general revelation is not sufficient for salvation, it is necessary for all Christians to participate in the Great Commission where Jesus told us to go out into all the world and make disciples of all nations (Matt. 28:18-20). This command of Christ, given by special revelation, is the command to give those who only have general revelation the more specific and necessary doctrines revealed through special revelation, the Bible.