These are good questions! A tall order, no doubt, but really important to think through. Together it strikes right at the core of the gospel message and great commission, the Shema Yisrael (Deuteronomy 6:4-9), the greatest commandments given by Christ (Mark 12:29-34; Matthew 22:34-40; Luke 10:25-28), and much of theology in the Epistles. While these capacities (heart, mind, soul, strength, and spirit) are difficult and cumbersome to delineate in exhaustive detail given the immaterial aspects of each, it is still relatively intuitive to understand because of the way each overarches and underpins our life. For example, you can faithfully re-articulate the Shema as ‘you shall love God with all that you are (soul), and all that you have (strength), and all that you can (heart)’. For a fuller explanation on the difference the heart and mind, click here.

Quick History of the Problem

There are many ways to go about defining these capacities, and I think it wise not to over-philosophize the text here. We are free to speculate, but not impose a scheme onto the text as a method of interpretation. That’s not to harp on anyone because it’s not self-evident either. In academia, this is called the constitution of man – it breaks down the human form into two parts: material and immaterial. Perplexed theologians have spent a long while trying to untie all the cultural, hermeneutical and theological knots to better understand how this immaterial stuff works –– is the soul different from spirit, or is it the same thing? Is the heart the seat of emotions, or is it the soul? Is the Bible referring to these immaterial things in the sense of function or substance? –– Needless to say, it’s not easy. It is also not quite clear if these are cultural or ontological (reality) distinctions, especially in regard to the semantic juggling between soul and spirit; since both words mean “breath” and seem interchangeable (Genesis 41:8; Job 27:3; Ecclesiastes 3:21; Daniel 7:15; Luke 1:46-47; John 12:27, 13:21), it really tightens the knots. This eventually led to three different views on the unity of the human composition, that is the immaterial nature or parts that make us human:

(a) Monism – 1 part: body-soul-spirit
(b) Dichotomy – 2 parts: body + soul-spirit
(c) Trichotomy – 3 parts: body + soul + spirit

Based on the Biblical data alone, and my understanding of the text so far, a variation of either the dichotomy or trichotomy view are sound, given the distinctions made in the New Testament.

1 Thessalonians 5:23 and Hebrews 4:11-13 both plainly state that there is a difference between soul and spirit, as well as body and heart, with particular importance to God’s final judgment. The Apostle Paul plainly says he desires for God to “sanctify you completely” (that is all of you) at the coming of our Lord, and explicitly states we ought to have our “whole” three parts blameless: body, soul, and spirit. If body, soul, and spirit are not distinct in their own right, then the clear terms used in Greek to thoroughly present a distinction between them sets aside its own integrity as nothing more than emotionally charged, fluffy talk. If so, specific verses in the NT may become somewhat meaningless when it says, “the word of God is living and active…. piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart.” (Hebrews 4:12) Because, well, there’s no division – at all! Either we forgo this integrity of this verse, or we allow emotivism to rule it in its place. Therefore, the dichotomy view can only work, from what I can tell, if and only if the soul and spirit have differing functions since each is of the same substance. So, let me highlight key aspects of each capacity that seem unique to itself.

What is the Spirit?

The words ruach and neshamah (Hebrew) and pneuma (Greek) all mean “breath, wind, or spirit”. From what I understand thus far, the spirit can be viewed as a blanket term for immaterial, incorporeal or spiritual stuff in general, from mental and moral attributes (Galatians 5:22-23, 6:1; 2 Timothy 1:7; 1 Peter 3:4) to its own kind of substance, from an individual person to a non-physical being (John 4:24; Luke 24:39). One example for how broad a term can be is the Hebrew word elohim, which refers to spiritual beings in general from God, angels, and demons to the disembodied dead (1 Samuel 28:13). God Himself is referred to as the Elohim of elohims (Psalm 82:1).

Spirit vs. Flesh

With such an open landscape, the simplest way to identify the spirit, in my view, would be to find its counterpart; whether that is complementary or a contrast in nature. This tells us what it is not; providentially, Jesus Christ, Peter, and Paul routinely contrast the spirit against the flesh (Mark 14:38; Luke 24:39; John 3:6-8, 6:63; Matthew 16:17; Romans 8:3-6, 13; 1 Corinthians 15:50; Galatians 5:17; 1 Peter 3:18, 4:6). I think it is relatively obvious that this is more than suggestive or playful language, they intend to emphasize that spirit is by nature a different substance, for lack of a better word, than flesh. The meaning of the flesh can range from anything-of-this-world and our bestial human nature to just the physical body in general. This is further revealed in 1 Corinthians 15:40-44 when Paul delineates between spiritual and physical substances: “There are also heavenly bodies and there are earthly bodies; but the splendor of the heavenly bodies is one kind, and the splendor of the earthly bodies is another…. It is sown a natural body; it is raised a spiritual body. If there is a natural body, there is also a spiritual body.” Paul reiterates this same contrast in regard to spiritual warfare as well: “For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places.” (Ephesians 6:12)

What is the Soul?

In Hebrew, the word nephesh (or sometimes neshamah) means “soul” or “(breath of) life”, which symbolizes the invisible force within living creatures (nephesh chayyah) that animates the body. In Greek and the NT, the word is psychḗ (literally soul, presumably derived from the verb psycho, “to blow”) is used in the Hebrew Scriptural sense, not in the Greek philosophical sense. While soul is strikingly similar to the definition of spirit, context helps dissociate the two. The soul is referenced mostly in relation to life itself, humans and animals alike (“nephesh behemah”), or even a dead body that once housed life (Leviticus 21:11; Numbers 6:6; Haggai 2:13). It is the lifeforce of a person/creature, which includes the body, “For the life [nephesh] of the flesh is in the blood” (Leviticus 17:11; 3 John 2). It is not limited to a biological body though, and can extend from physical to spiritual, from this world to the next (Genesis 35:18; Matthew 10:28; Acts 3:23; Hebrews 6:19-20). This is made clearer in Acts when roughly three thousand “souls” were baptized and added to God’s Kingdom (Acts 2:41-43) or when Peter says in the days of Noah, “eight persons [souls, psychḗ], were brought safely through water.” (1 Peter 3:20). Since life or lifeforce are broad sweeping terms, the words nephesh and psychḗ can also refer to a “person” or “living being/creature” (Genesis 2:7; Leviticus 5:2; Ezekiel 18:4; 1 Peter 3:20; Revelation 18:13, 20:4), as well as in the sense of a self-reflecting agent such as “myself”, “himself” or “themselves” (Psalm 16:9-10; Jeremiah 13:7; 1 Samuel 22:2), but this does not seem to include personality traits from what I can tell so far (perhaps it does). While it does include emotional qualities, it is more so deep-seated bedrock feelings that intensely affect our sense of life or self, such as sorrow (Psalm 42:6; Matthew 26:38; Mark 14:34; Job 30:24-31), anguish or despair (Deuteronomy 28:65; Judges 16:16; Psalm 43:5), resentment, hatred, or evil (1 Samuel 30:6; Proverbs 21:10, 23:2), deep affection, intimacy, or brotherly love (1 Samuel 18:1-3, 20:17; Song of Solomon 1:7, 3:1-4; Jeremiah 12:7), feelings of overwhelming joy in God (Luke 1:46-47), deep desire for salvation and God (Genesis 23:8; Psalm 63:1, 5, 8-9; 119:81), sexual desire or spiritual lust (Genesis 34:3; Exodus 15:9; Jeremiah 2:24), courage in the face of death (Judges 16:30), and so forth. With all this in view, the soul seems to be the bedrock of the living self, the deepest sense of life and “I am”.

Soul vs. Spirit

A crucial passage to delineate between soul and spirit is in none other than the greatest commandments demarcated by Jesus: “And you shall love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.’ The second is this: ‘You shall love your neighbor as yourself.’” (Mark 12:30-31)

This command to love is not limited to spiritual things alone, it is a full expression of being; it extends from body to spirit, physical to spiritual. The soul, then, is among the list of things that love can or may supersede, whereas the spirit and body are not listed; the body and spirit are things the soul operates in. In short, body and spirit are the bookends of two different substances (cf. 2 Corinthians 7:1; Ecclesiastes 12:7). From what I have gathered so far, there does not seem to be Scriptural warrant or indication that the soul can supersede the spirit, like the spirit which supersedes body (cf. James 2:26). The soul somehow connects the spiritual to physical; that is, the spirit to flesh. This could be why the author of Hebrews parallels the spirit to marrow and soul to “joints” (4:11), using two similar biological things to show how similar the two spiritual things are, and yet the word of God can still split the difference come judgment day (v.13). The spirit, then, may be the permanent house of the soul; for upon death the soul returns to solely spiritual substance but will be resurrected with the flesh on that day. Jesus also pairs the soul and body/flesh together on several occasions as part of judgment and condemnation (Matthew 10:28; Matthew 16:26; Mark 8:36-37).

As a matter of interest, the concept of saving your soul is often said (James 1:21, James 5:20; 1 Peter 1:9; Matthew 10:28; Mark 8:36-37), but saving your spirit is only mentioned once in reference to a Christian sinning profusely (1 Corinthians 5:5), and might be where the most fundamental self is housed (cf. 1 Corinthians 3:10-15). So, soul and spirit can be used synonymously, but that does not mean they are the same thing. For instance, like the Hebrew word elohim mentioned earlier, the word angel (angelos) means “messenger”, but is sometimes used in the NT as a blanket term for heavenly bodies in general (1 Corinthians 4:9, 6:3, 11:10, 13:1; 2 Thessalonians 1:7-8; 2 Peter 2:11), even though all the apostles know that not all heavenly bodies are messengers (i.e. cherubim, seraphim) and angelos can apply to people, also (Luke 7:24; 9:52; Mark 1:2-3; James 2:25). I suspect the word spirit likewise applies as a blanket term for immaterial aspects, which can include the soul (even heart and mind).

The spirit can also directly affect the soul in, say, deep emotional, psychological or moral feelings such as love (1 John 4:7-21; Galatians 5:22-24; Colossians 1:7-8). Living in the Spirit produces the fruits of the Spirit in your life, such as love and truth, since God is both by definition. The soul is not marked among these qualities, or at least, it is not identified as the source of these qualities.

To sum this section up, the fact that Jesus, Peter, Paul, and every other apostle contrast flesh against spirit yet never contrast flesh and soul is significant, as if the soul is subjugated to the flesh in some respect. They do though indicate a conflicting relationship of sinning in the flesh, one that condemns and wages “war against your soul” (1 Peter 2:11), but they do not make an explicit ontological juxtaposition, as if the soul is independent of the flesh like the spirit is; they are different substances from different places: one earthly, the other heavenly (1 Corinthians 15:50-53). As mentioned before, Paul clearly delineates between all three, which leads me to believe the soul is somehow the “joint” in between, if you will. Perhaps a faint analogy, but sort of like white light shining through a prism. If white light is spirit and the prism is body, then colour is soul.

What is the Heart?

The word heart is levav in Hebrew and kardia in Greek. Biblical writers reference the heart in ways that pertain to matters of belief, behaviour, conscience, moral character, courage, will, understanding, passions, intention, desire and so on. It overlaps with the function of soul and mind in a lot of ways, especially in the Old Testament; the heart and soul together implied mind. At any rate, there still seems to be a central role of the heart itself.

According to Jesus, the apostles and prophets, the human heart is evil (Jeremiah 17:9; Mark 7:21-23; Matthew 15:18-19). Because the heart is a soft fleshly substance in physical terms, it is metaphorically “hardened” and likened to a stone, where only God can give you a new heart of “flesh” (Psalm 51:10; Ezekiel 36:26; Mark 16:14; 2 Corinthians 3:2-3; Ephesians 4:18; Hebrews 3:8, 3:15, 4:7). And unlike the contrast made between spirit and flesh, the flesh is a very good thing here. This transformative expression of stone to flesh is important, and eschatologically suggestive in regard to new creation (baptism and resurrection); even the flesh is redeemable in Christ (hence, Paul’s use of sanctifying the whole person, body included, cf. 1 Thessalonians 5:23; 1 Thessalonians 3:13; Jesus even warns of soul and body in hell too, Matthew 10:28).

We are held accountable for the intent, thoughts and desires of our heart. Belief is usually credited with the heart, too (Hebrews 3:12; ; Mark 11:23; Luke 8:12, 24:25; John 14:1), and true belief leads to action, “For with the heart one believes and is justified, and with the mouth one confesses and is saved” (Romans 10:9-10; Ephesians 6:6; Acts 4:32). We also see this belief-to-behaviour parallel when God says He will “circumcise your heart” (Deuteronomy 30:6) and the Apostle James’ famous passage of faith without works is dead testifies that true belief produces action (James 2:18-26). The heart often indicates the filter and flow of action – what you can do – from internal to external and vice versa (Matthew 15:18-19). The central role of the heart, then, is belief and behaviour. It is our moral constitution.

As the Proverbs say, “Above all else, guard your heart, for everything you do flows from it,” or “for from it flow the springs of life.” (Proverbs 4:23; cf. John 7:38) If you guard your heart with goodness, with Godliness (Ephesians 6:10-18), you will do well.

Do we live forever?

The short answer is yes. I’ve run out of space to deal with this topic in sufficient detail, so let me leave you with some study passages (I recommend using Blue Letter Bible and BibleGateway for quick research).

• “Eternal Life” prooftext: Mark 10:17-31; Luke 10:25-37; John 3:15-16, 17:3
• “Eternal Punishment” prooftext: Daniel 12:2; 2 Thessalonians 1:9-10; Jude 1:7; Revelation 20:10, 14-15

In essence, there is no reason to doubt the traditional view of the afterlife, even if annihilationism or universalism is possible. If God chooses to do otherwise, that is His prerogative, not ours. For now, it’s best to bank on what we know: “Then they will go away to eternal punishment, but the righteous to eternal life.” (Matthew 25:46)

In Luke 10:25-28, the teacher of the law asked Jesus, “what must I do to inherit eternal life?” Jesus points to the greatest commandments (cf. Mark 12:30-31). That said in a contemporary way: ‘You shall love the Lord your God with all that you are (soul), all that you have (strength), all that you can (heart), and all that you could (mind). And the second is like it: ‘You shall love your neighbour as yourself.’

This is not a perfect answer by any means, but I hope it helps! I will more than likely update this entry in the near future as I study through the Scriptures further. God bless, GH!!