What, then, is the heart? The heart is not a separate part in addition to the soul and the spirit; rather, it is a composition of all the parts of the soul and the first part of the spirit. It includes the mind, the will, and the emotion plus one part of the spirit, the conscience. The shaded area in the following diagram illustrates the parts that compose the heart.
Man does not have more than three main parts in his being. As a human being we have a body, a soul, and a spirit. We do not have a fourth and separate part that is called the heart.
Now we need to confirm that the mind, the first part of the soul, is a part of the heart. In Matthew 9:4 Jesus said to the scribes, “Why are you thinking evil things in your hearts?” This indicates that one can think in his heart. Since the thinking processes are in the mind, this proves that the mind is a part of the heart. Genesis 6:5 refers to the thoughts of man’s heart. The thoughts are of the mind, but Genesis 6:5 speaks of the thoughts as being of the heart. Hebrews 4:12 also refers to the thoughts of the heart. These three verses are ample proof that the mind, an organ of the soul, is a part of the heart.
Acts 11:23 refers to the will. In this verse Barnabas encouraged the believers in Antioch “to remain with the Lord with purpose of heart.” To purpose is a function of the will, but in Acts it is referred to as being of the heart. This shows that the will also is a part of the heart. Hebrews 4:12 speaks of the “intentions of the heart.” The intentions correspond to the purposes, which are of the will. Again, this proves that the will is a part of the heart. There are more verses, but these two are sufficient. According to the scriptural standard, only two witnesses are required (Deut. 19:15; John 8:17).
In John 16:22 the Lord said to His disciples, “Your heart will rejoice.” To rejoice is an element of the emotions, but here the Lord said that the heart rejoices. This confirms that the emotion also is a part of the heart. In the same chapter the Lord said, “Sorrow has filled your heart” (v. 6). Sorrow also is something of the emotion. Hence, these two verses verify that the emotion is a part of the heart.
Concerning the conscience, Hebrews 10:22 says, “Having our hearts sprinkled from an evil conscience.” Here we see that the conscience has much to do with the heart. In order to have a pure heart, we must have a conscience that is without offense. Our conscience must be sprinkled with the blood of Christ in order for us to have a pure heart. Thus, without a doubt, the conscience is a part of the heart. First John 3:20 says that “our heart blames us.” To blame is a function of the conscience. Hence, this verse proves that the conscience is a part of the heart.
Scriptural ground has thus been given to prove that all the parts of the soul—the mind, the will, and the emotion—and the first part of the spirit—the conscience—composed together equal the heart.