The heart is central in Orthodox Spirituality. This is biblical: if your heart is pure, your actions are pure. If your heart is impure, so will your actions be.

In our Orthodox tradition, the heart is bigger than the mind and the mind is located in the heart; the combination is referred to as the nous (νους). The heart is not identified with the physical heart, but it is understood to be the center of our spiritual existence.

God takes up residence in the heart (Galatians 4:6; Ephesians 3:17). Christ refers to this residency in the heart as “the Kingdom of God,” which is not a state like New Mexico or Montana, but rather may be understood as a  reign  or  rule (βασιλεία). It is a verbal noun; it is not, in other words, static but energetic. When Christ says, “The Kingdom of God is within you” (Luke 17:21), he means that we are energized by God’s power through the Holy Spirit. This is where we know the “peace of God that passes all understanding” (Philippians 4:7), to which Paul also testifies at Romans 5:5. In the heart we receive both the grace of God and the enlightenment of our lives (II Corinthians 4:6).

The heart is the location for our feelings, for our will, and for our thinking.

Our objective as Christians is to have these three unified, for the heart to be one. Sin interrupts this process of unification. The mind may be convinced of the good, but the will is not able to follow because of the heat of desire; hence, the unity of the heart is broken.

When trouble comes, it comes in the form of double-mindedness (this concept is found in the Epistle of James, chapters 1 and 4, in particular). We are split apart in consciousness. Jesus uses a different metaphor for the same idea in Matthew 6:22: “The lamp of the body is the eye. If therefore your eye is good (sound, singular), your whole body will be full of light.” We are to be of one mind and focused. But we do not see the world aright because we are blind. The Slavonic word for this problem is  prelest, or delusion or, better still, spiritual blindness. Ironically, the word has the positive meaning of “lovely” in the sense of “enchanting.”

Because of the dynamic nature of our lives and our hearts, and because we are always strung between good and evil, light and darkness, life and death (see Deuteronomy 30:19), the Evil One may also take up residence in the heart. We may be deluded; we may be spiritually blind; we may not think right! The Orthodox Tradition, however, insists that the Light cannot be overcome (see John 1) by the darkness that Evil brings to it. Because of baptism, our hearts are filled with the grace of God that cannot be extinguished; therefore, the Evil One cannot take up residence in the heart but must remain outside as a goad (St Diadochos of Photiki, On Spiritual Knowledge, Philokalia Vol. 1). Metaphor or not, this is a powerful image that can bring us comfort in dark moments.

The heart is the seat of passion (pathos - πάθος). As our Lord says, “Out of the heart proceed evil thoughts” (Matthew 15:19). Paul writes, “Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires” (Galatians 5:24) and goes on to list the virtues of life in the Spirit. But this is again part of the dynamic of life. There is no guarantee that we will remain in this condition; in fact we have every reason to commit ourselves to spiritual warfare for life. At the heart of this is the struggle for self-control (Galatians 5:23, Ephesians 4:22, and elsewhere) and for what the Tradition calls  apatheia (απάθεια), which means dispassion; it does not mean that we become apathetic, but that we view all things without clinging to them. In a way it relates to our use of the icon. Our vision does not stop with the icon; if it does, then we do indeed make an idol of the icon. Our vision must pass through the icon to see the reality it embodies.

At this point we must consider the process of temptation. The Fathers of the Philokalia clearly labeled this process. We should learn to recognize it in our own lives. At the core of the process is a  logismos, (λογισμός) a thought that potentially leads to action. First there is the suggestion to sin. A temptation arises: let’s be gluttonous. Let’s gorge ourselves on food and wine. Wow! Great idea!  Second, we begin to think about this suggestion, savor it, interact with it, and dwell on it. Third, we accept the premise as possible (to change the temptation: I can find a way to commit adultery with that person). Fourth, we enter into agreement with the suggestion (I want to commit adultery with that person), and we become captive to it. The thought becomes habitual and we become passionate about it. The Fathers say that this is the point when it becomes sin, in accord with Christ’s word (Matthew 5:28). We don’t have to fulfill the act. We have already stepped over the line, and we must repent and repeal our agreement to the suggestion. We must refuse the logismos with its allure. Now, back to our concern with the heart.

“Blessed are the pure in heart, for they shall see God,” says our Lord. The first step toward purification of the heart is the recognition that we need God’s power; we cannot purify ourselves. We can only invite this act of Grace into our lives. We can turn to it but we cannot purify ourselves.

The logical second step, then, is prayer. The Fathers particularly invite us to the Jesus Prayer. This prayer is performed in quiet (Greek  ησυχία hesychia  – hence, the term hesychast prayer), an injunction that goes back to Christ’s word at Matthew 6:5-6. Since this prayer penetrates deep within us, it is also called noetic prayer, i.e. the prayer of the nous, in this case the word meaning that supplication which embraces both mind and heart (see Mark 12:30).

Repentance (metanoia - μετάνοια) is the next step. Repentance means, literally, re-thinking: we have to enter into the depths of our own hearts to discover all those habits and temptations to which we cling that separate us from God’s Light. This is the capsule sermon with which Jesus begins his ministry, according to Mark 1:15, “The time is fulfilled. The Kingdom of God is at hand. Repent, and believe this good news.” Reflection on the Love of God draws us to repentance (Romans 2:4).

There is the possibility of return. As we pray at the Divine Liturgy, “Shine in our hearts, Loving Master, with the pure Light of your divine knowledge and open our hearts to the message of your Gospel.”

In the Orthodox tradition, a great deal of emphasis is placed upon tears of mourning for our alienation from God. This is called  penthos (πένθος)  in Greek; the word is the opposite of acedia (ακηδία), which means sloth or despair. Hence these are not tears of despair, but rather of mourning at the loss of paradise, so to speak, in our own lives. St Isaac the Syrian wrote much about the gift of tears, but he is one among many of the fathers who recognized the importance of mourning at loss.

If we desire purity of heart, we must see that the worship life of the church is of central importance. Simply put, we make no solo progress along this pathway; we join together with others in community in the knowledge that we are all seeking purity of heart. We need the sacraments and the Word of God to nourish us and to enable us. The ascetic life includes fasting. This is important but we must always remember that the fast is of the soul as well as the body. Bodily fasting is only the outward manifestation of inward fasting. If it is only outward, the fast is worthless (see Christ’s word at Matthew 6:16-17).