Sources of Assurance

We continue our series on the blessed but difficult subject of assurance of salvation (see part 1). Assurance or certainty about a truth in general may come in various ways, such as seeing or hearing something with your eyes and ears, knowing a first principle and making logical deductions from it, or receiving a witness that has authority. No authority is higher than God’s revelation. What kind of certainty can the people of God have about their being in Christ? It is a mixed kind of certainty, partly based on faith in God’s Word, and partly by a spiritual sense and experience worked by the Holy Spirit.
A man who lives in the habit of serious sins should be assured that he is presently in a damnable condition, and will be so as long as he lives that way. The works of the flesh are manifest or plainly visible, and those who live that way have no inheritance in God’s kingdom (Gal. 5:19–21). If this is your life, do not flatter yourself but wake up. However, no one has warrant to be assured that he is eternally rejected by God, for the Bible does not tell the names of the reprobate and God does not reveal such things directly to anyone.
No one by his natural powers of understanding can come to an assurance of saving grace in his soul. No one can see the sun except by the light of the sun; no one can see Christ in his soul except by the Spirit of Christ. He is the Spirit of adoption who assures the believer. This is why God’s people have spiritual combat, not only between sin and holiness, but also between doubt and faith.
A Christian may be assured in this life of four special mercies: election by God, forgiveness of sins, sanctification of his nature, and perseverance in holiness unto future glory. However, the foundation of all the others is assurance of our sanctification. There can be no certainty that God predestined us, justified us, and will glorify us, unless there is certainty that God has made us new within and we see the fruit of sanctifying grace.
It is a very sad delusion when an ungodly man is persuaded that he is in a state of grace, when in fact he is in a state of sin and death. This is worse than being possessed by demons. It is like the condition of the church in Laodicea, who thought they were rich and full, when they were naked and empty (Rev. 3:17). It is like the condition of an insane man who thinks he is a prince with a large estate but in fact is locked in chains in a dungeon. Therefore beware lest your self-love blind your eyes and harden your heart, and pray for God to make you know yourself.
The soul of man has two kinds of acts. One kind is direct acts, as when I take Christ and cling to Him by faith. The other kind is reflective acts where a man perceives his own direct acts, as when I perceive that I cling to Christ and love God. Certainty or assurance is a reflective act, a feeling or perceiving of one’s own faith.
The assurance of a believer is within his own heart and cannot be made known to another person. Just as only those who have been a father or mother understand what it is like to have such a relationship, so this certainty is only for those who have experienced it. It is compared to a white stone that no one knows except the person who has it (Rev. 2:17). We can have a judgment of certainty towards ourselves, but only a judgment of charity towards others.
The certainty of all acts of faith, whether direct or reflex, depends more upon the work of God’s Spirit than the evidence. Christians can have a firm faith in the Scriptures by the power of the Spirit even when they cannot answer all the arguments of their persecutors. In the same way, a believer’s confidence  that he has real, saving grace depends more upon God’s Spirit releasing him from fear and bondage than it does upon the greatness and beauty of grace within him.
A human being in his natural life knows his natural motions to see, hear, touch, feel, taste, and think. In the same way, a Christian in his spiritual life knows his spiritual motions to love his brothers and God (1 John 3:14). However, natural motions are not opposed by temptations, but spiritual motions are and thus are more difficult.
The Bible speaks of this certainty with words such as persuaded (peithō), know (ginōskō), faith (pistis), confidence (pepoithêsis), boldness (parrêsia), and assurance (plêrophoria). We must be careful however not to confuse faith, confidence, and assurance—as some theologians have done. One may have justifying faith without assurance. Ephesians 3:12 teaches us that faith has three effects: confidence, boldness or assurance, and freedom to draw near to God in prayer as one welcomed by Him. Some say that faith, confidence, and assurance are the same thing in three different levels of maturity. Others say they are distinct graces. 
So do not let your heart despair if you have not attained to assurance. The God that has made you desire Christ, and who has supported you in your doubts and fears, can bring you to assurance one step at a time. In the end your doubts may produce a much stronger faith, as trees shaken by the wind will have stronger roots. In fact, the Christian’s assurance is not so high and full that it excludes all doubting. Nothing in this life is perfect, whether it be our obedience or comfort. Our certainty will be painfully assaulted by Satan and our own unbelief. We may even say that he who never doubted, never believed. There is some bitterness in all our honey.
Joel Beeke