Jeramiah 17:9 says “The heart is deceitful above all things, and desperately wicked: who can know it?”
My question is, is our heart in itself evil, or is it because of the fallen angels making it that way?
Man has a fallen nature via original sin. But with via Christ he is given a “new heart” …and becomes a temple of the Holy Spirit…
When a person is “in Christ” his heart is good…there is still concupscience to struggle with…but being in Christ he has been given a new heart…and if he commits a mortal sin…he can return to Grace via confession…and be renewed in heart…
From the Catechism
2563 The heart is the dwelling-place where I am, where I live; according to the Semitic or Biblical expression, the heart is the place “to which I withdraw.” The heart is our hidden center, beyond the grasp of our reason and of others; only the Spirit of God can fathom the human heart and know it fully. The heart is the place of decision, deeper than our psychic drives. It is the place of truth, where we choose life or death. It is the place of encounter, because as image of God we live in relation: it is the place of covenant.
a few ways the Catechism uses the term Heart…just a a few…to see there is much to the term “heart”
1432 The human heart is heavy and hardened. God must give man a new heart.25 Conversion is first of all a work of the grace of God who makes our hearts return to him: "Restore us to thyself, O LORD, that we may be restored!"26 God gives us the strength to begin anew. It is in discovering the greatness of God’s love that our heart is shaken by the horror and weight of sin and begins to fear offending God by sin and being separated from him. The human heart is converted by looking upon him whom our sins have pierced:27
2517 The heart is the seat of moral personality: "Out of the heart come evil thoughts, murder, adultery, fornication. . . . "305 The struggle against carnal covetousness entails purifying the heart and practicing temperance:
Code:
Remain simple and innocent, and you will be like little children who do not know the evil that destroys man's life.306
2532 Purification of the heart demands prayer, the practice of chastity, purity of intention and of vision.
2559 “Prayer is the raising of one’s mind and heart to God or the requesting of good things from God.” But when we pray, do we speak from the height of our pride and will, or “out of the depths” of a humble and contrite heart? He who humbles himself will be exalted; humility is the foundation of prayer, Only when we humbly acknowledge that “we do not know how to pray as we ought,” are we ready to receive freely the gift of prayer. “Man is a beggar before God.”
2645 Because God blesses the human heart, it can in return bless him who is the source of every blessing.
1431 Interior repentance is a radical reorientation of our whole life, a return, a conversion to God with all our heart, an end of sin, a turning away from evil, with repugnance toward the evil actions we have committed. At the same time it entails the desire and resolution to change one’s life, with hope in God’s mercy and trust in the help of his grace. This conversion of heart is accompanied by a salutary pain and sadness which the Fathers called animi cruciatus (affliction of spirit) and compunctio cordis (repentance of heart).
2608 From the Sermon on the Mount onwards, Jesus insists on conversion of heart: reconciliation with one’s brother before presenting an offering on the altar, love of enemies, and prayer for persecutors, prayer to the Father in secret, not heaping up empty phrases, prayerful forgiveness from the depths of the heart, purity of heart, and seeking the Kingdom before all else. This filial conversion is entirely directed to the Father.
2621 In his teaching, Jesus teaches his disciples to pray with a purified heart, with lively and persevering faith, with filial boldness. He calls them to vigilance and invites them to present their petitions to God in his name. Jesus Christ himself answers prayers addressed to him.
2083 Jesus summed up man’s duties toward God in this saying: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.” This immediately echoes the solemn call: “Hear, O Israel: the LORD our God is one LORD.”
God has loved us first. The love of the One God is recalled in the first of the “ten words.” The commandments then make explicit the response of love that man is called to give to his God.
also on the passions…
vatican.va/archive/catechism/p3s1c1a5.htm