Dr. Looyenga is Professor of Chemistry and Biochemistry at Calvin College and is a member of Zion Protestant Reformed Church, Hudsonville, Michigan.

“And Jesus answering said unto them, They that are whole need not a physician; but they that are sick. I came not to call the righteous, but sinners to repentance.” Luke 5:31, 32

I recall a conversation I had with a certain Dr. John Marcus when I was a college student learning how to do cancer research. And yes, this is the same man who is now serving as pastor of First PR Church of Edmonton. At the time we talked, Rev. Marcus was working as a research scientist at the Van Andel Institute in Grand Rapids. Over lunch we conversed about our future career plans, and I expressed my surprise to him regarding his pursuit of the ministry after having invested nearly a decade in scientific training. He simply smiled and said that he felt called to help fight a different kind of disease than the one he was currently working on as a scientist.

At the time, I understood what he meant. Somewhat. Clearly, the future Rev. Marcus was referring to diseases of the soul, the kind that need the Great Physician and not a human doctor. But, at the same time, I do not think I really understood the depth of his analogy. In part, this was because I was young and naïve regarding this world and its sins; but it was also because I had only just begun the work of researching the disease we call cancer.

Looking back at that conversation today, I can see how very insightful this analogy truly is. Like many of the symbolic relationships presented in Scripture, the representation of sin as a disease has far more depth than most of the simple analogies we draw from our own experience. Both diseases and sins come in a bewildering variety of forms that are more or less evident in the lives of the afflicted. Some sins are acute, heat-of-the-moment sins that we realize and repent of almost as soon as we commit them—like a quick bout of flu that comes and goes in just a few hours. Other sins are more like chronic infectious diseases. These symbolize the besetting sins that plague us for a lifetime, needing constant spiritual attention and repentance on a near daily basis. Some sins are like blindness, dimming our view of Christ and the glory of our Father in heaven. Others are like dementia, causing us to forget the promises of the gospel and the hope of life eternal. No matter the sin, we find pain and misery that only has one true cure—the cross—and the only physician—our Lord Jesus Christ.

I have no doubt that an entire book could be written on how each disease of the body has unique similarities to a specific sin, especially since Scripture mentions quite a wide range of different maladies, each of which is its own picture of sin. From my own experience, however, I especially see cancer as a remarkable representation for sin. Not only are the specific features of cancer applicable here, but so too are the therapies used to treat this dreadful disease. Furthermore, our collective experience with this disease is vast—almost every reader of this article has likely been touched by cancer, sometimes very directly. We know friends, family members, and other loved ones who have suffered from or succumbed to cancer, and it is an all-too fearful fact that many of us will face this disease personally.

Cancer takes on an especially personal dimension in comparison to other diseases because it emerges from the cells of a patient’s own body. Cells that become cancerous arise progressively from normal tissues that accumulate genetic damage from a variety of sources, including those external to the body (UV light, chemicals) and those internal to it (metabolic byproducts of oxygen). We will return to the progressive nature of cancer later, but here I would point readers to the fact that cancer arises from an internal process of corruption within the body. As such, it is a disease that is unique to each person at the genetic level, which has led to the realization that each patient really needs to be evaluated and treated according to his or her own unique cancer.1

The intrinsic—or personal—aspect of cancer provides an especially good comparison to sin if we think of the analogy in terms of the threefold enemy of believers. In this context cancer best represents sin that arises from our own fallen nature rather than that which arises from the external work of Satan and the world upon our souls. In many ways our individual besetting sins are so personal because they seem to emerge out of the very fiber of our character. Consider, for instance, the man to whom God has given the gift of leadership. He may serve confidently and wisely in church office, or perhaps as a member of school boards and other committees doing kingdom work. For such a man—gifted and confident—the sin of pride is an ever-present foe, tempting him to turn God’s providence into an occasion for personal glory. This is not the only example that we can envision, since our greatest personal gifts often become the conduit to our worst spiritual liabilities. Our sins flow out of our nature, each individual believer battling the depravity clinging to his or her own unique character.

Just as physicians have to be able to diagnose the kind of cancer they are treating in order to know what they should expect during the treatment process, so we have to be aware of our own God-given personality to realize the sorts of besetting sins to which we are most liable. Doing a regular “spiritual diagnosis” through Scripture study and prayer is key to our recognition of what we need to confess before God, and for what we should seek His forgiveness (Ps. 139:23, 24; II Cor. 13:5). When we know what we are fighting at the spiritual level, we are better able to respond to the treatments that God has prepared to root the cancer of sin out of our souls.

The predictive ability of a physician to know what sort of cancer a patient is at risk for developing is an important aspect of treatment, but so too is the work of medical pathologists who use visual images of cancer biopsies to diagnose the type and severity of tumors. Pathologists often describe cancer with words that are chillingly descriptive of how awful this disease can be for patients. These words are worth noting because they can just as easily be used to describe how sin works on our souls. Understand that this is not just dramatic language meant to overemphasize the analogy between cancer and sin. The awful nature of this disease should remind us that sin is not some benign weakness or temporary inconvenience to our spiritual life—it is truly a life-threatening corruption that, if left untreated, can kill us spiritually.

Cancer is often described as an insidious disease, one that almost imperceptibly begins to grow within the body before the patient realizes something is wrong. Quite often the process of cancerous growth begins slowly, progressing over a long period of time during which a patient has few—if any—symptoms that would suggest something is wrong. Much of the routine screening done in modern healthcare is aimed at catching cancers early in their progression, before they develop into a malignant and destructive tumor. Tumors that have begun to extend finger-like projections of cells into the normal tissue environment surrounding them—a process called invasion—are defined as being malignant, whereas tumors that remain clearly separated from normal tissue are considered benign. It is, in fact, the claw-like invasive features of this disease that lead to it being called cancer, the Latin word for “crab.”2 Invasive tumors are far more difficult to remove than most benign tumors, and worst of all, they may not stay in their original tissue location. Invasion of cancer cells into the bloodstream or lymph nodes allows them to spread to distant locations in the body in a process called metastasis. It is quite often these secondary tumors that cause the biggest problem for cancer patients, as they are much harder to find and treat than the original tumor. While the actual cause of death for patients can vary widely, cancerous tumors tend to be metabolically parasitic, slowly draining patients of the energy and nutrients they need to remain healthy.

Each of the words italicized in the preceding paragraph can equally be used to describe sin. Sin is insidious in character; we often do not even realize its seriousness because the consequences early on may be few, and the sin is hidden to others around us. Sin is also progressive in our lives. Very rarely does sin begin as a single, massive event. More often it emerges slowly as a gradual—and perhaps unnoticeable—moral slide. An extra look at the sidebar ad on an otherwise decent website. One click. Then another. And so on. How often is this not the pathway to a fall into the sin of pornographic addiction, or gambling, or gossip—or a whole list of other sins? Sin is deceptively insidious and progressive as it emerges from our fallen nature to entangle us.

Once it has its hold, sin becomes progressively malignant in our lives. All sins can be addictive to our fallen human nature, capable of capturing our minds and bodies in such a way that our souls too become completely ensnared. In the absence of Spirit-led intervention, sin inevitably invades into our life, slowly choking out the desire for God’s Word and progressively stealing time away from the activities that should characterize the life of a believer. Prayer? Scripture reading? Meditation? Service to family and church? There is no time left for these vital activities when a sin has its hold on us. Like an invasive cancer, it spreads to our every thought and motivation, draining away our spiritual energy so that nothing is left of our covenant relationship with God. Such is the way of terminal sin—it is like a parasitic organism growing within us, slowly choking away our spiritual life.

And it is not only the spiritual health of individual believers that is at risk to the malignancy of sin; so too is the health of a much larger organism—the church. The apostle Paul often described the church as a body made up of distinct parts with distinct functions (I Cor. 12; Eph. 1:20-23). Within this symbolic language we understand that the church is the figurative body of Christ, united to its Lord by faith through His work on the cross. Until the final resurrection, however, this body is still susceptible to the ravages of sin. It should not escape our notice that many of the New Testament epistles were specifically written to combat sins that were creeping into the early church. Though Paul used a different biological analogy to describe sin in Galatians 5:9 (growth of yeast in bread dough), his point is abundantly clear. Sins—in particular false teachings—have a way of spreading through the body of Christ like a metastatic cancer, threatening to choke out the life of congregations once committed to the truth of Scripture. Sin is not just a personal threat; it is a danger to the entire body of Christ on earth.

But take heart, believer, because there is treatment for the spiritual cancer of sin! In His grace God has provided a way out of every sin and temptation, and a treatment that is fitting to the disease that has invaded your soul. In this respect, we can continue to use cancer as an analogy for sin, but now from the point of view of how a physician would prescribe treatment for cancer. So now we turn to the therapies for cancer, and how they point us to the work of the Great Physician who operates—as it were—by the work of His Holy Spirit.

Surgery is the first line of treatment for many cancers. The goal of surgical treatment is to cut cancer out, removing it entirely from the body. Such is the purpose of God’s Word relative to sin in our lives. The author of Hebrews even compares the Word of God to something like a surgeon’s scalpel, “sharper than any two-edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow…a discerner of the thoughts and intents of the heart” (Heb. 4:12). Like a scalpel in the hand of the Spirit, the Word exposes and cuts away the sins of our soul. Thank God for this tool, for without it we would be unable to escape the spiritually deadly growth of sin in our fallen flesh.

A similar mode of treatment is prescribed by Scripture for the cancer of sin that threatens to metastasize more broadly into the body of Christ (Matt. 18:15-18; I Cor. 5:1-13). In this case, Christ gives the power of the scalpel to His church to remove from itself one who walks impenitently in sin, refusing to be admonished (Matt. 16:19). This is the tool of excommunication, which is intended to turn a sinner from his sin, but also to preserve the spiritual health of the broader body of believers in a church. As explained in Lord’s Day 31 (Q&A 83-85) of the Heidelberg Catechism, excommunication prevents the spread of sinful doctrines or practices, effectively removing this disease before it can produce broader sickness in Christ’s spiritual body. Thankfully, it is a tool that is used in sparing measure, but one that is nonetheless presented as a remedy for sin in the church.

Despite their clear power against cancer, scalpels are not the only instruments in the Great Physician’s hand. Especially when the deadly growth of sin has spread into our lives like an invasive cancer, a harsher therapy may be needed in addition to the Word. Chemotherapy and radiation therapy are radically harsh, painful, and even destructive means to treat a cancer patient. They involve the use of toxic chemicals and damaging energy beams to essentially poison or burn away surgically inaccessible cancer cells. We know the side effects of this treatment: nausea, hair loss, burns, and other more long-term effects. But we count these effects worth bearing when they mean life for the patient.

So too the tool of chastisement in the hand of God. When applied to the sinning believer, chastisement is never pleasant, or even free of “side effects” in our lives. We feel pain acutely under such circumstances, but that pain is necessary to treat a life-threatening disease. Sin may not be left to relapse; it must be removed at all costs! Our Lord must have shocked His audience when He told them it would be better to amputate a limb or gouge out an eye than to allow that organ to lead them into deadly sin (Matt. 18:8,9). Such is the effect of chastisement in our lives. It may come with permanent scars or life-long disability—physical or spiritual—but for the sparing of life it is worth bearing. When such a chastisement is the tool God chooses to expunge the lingering sin from your soul, say with David “let [me] fall now into the hand of the Lord; for his mercies are great” (II Sam. 24:14).

The three therapies for cancer described above are external sources of treatment for cancer that require the application of a completely foreign device or drug to patients. Though effective in many ways, these forms of treatment often fail in especially aggressive cancers that have metastasized throughout the body. In the last few years a new form of cancer treatment called immunotherapy has become a standard weapon in the fight against cancer. This approach is revolutionizing the field of oncology because it works remarkably well for late-stage cancer patients. As its name implies, this form of treatment harnesses a patient’s own immune system to fight cancer, but with little of the toxicity associated with more traditional treatments of chemicals and radiation. And though this form of therapy takes a variety of forms, they all share the common purpose of rousing a robust immune response that can seek and destroy single cancer cells throughout the entire body.

Like the other treatments for cancer, immunotherapy has a clear parallel to God’s treatment of our sins. Just as this form of therapy seeks to rouse in the patient an internal response to the presence of disease, so too does the Holy Spirit quicken in God’s children the “new man” in Christ (Col. 3:10; Eph. 3:16). But rather than using a therapeutic drug to stimulate the new man, the Spirit applies the means of grace as His treatment for an ailing sinner. This making alive of the mind and spirit in a redeemed believer not only enables him to recognize his sins (Eph. 4:22-24), it also creates in him the ability to fight sin and temptation by actively pursuing the will of God (I Pet. 4:2). The quickening of the new man, therefore, seeks and destroys sin in our lives, making us alive in Christ rather than dead in sin (II Cor. 5:17). What a power, that God can rouse in us the ability to fight the deadly disease of sin, clearing it from our souls so that we can again experience a healthy covenant life with Him!

Which therapy is the one you need in your life, believer? What cancer lurks in your soul, needing to be rooted out and destroyed by the work of the Spirit? I do not know and perhaps you do not either—but the Lord does! As the Great Physician, He has an entire collection of specialized scalpels and therapies that can be used to heal you of sin. As we noted earlier, no cancer is the same, which has led to the recognition by modern physicians that what we really need to treat this disease is “personalized medicine.” This is what our gracious Lord uses to treat our weaknesses and besetting sins (Heb. 12:1; Ps. 139:23, 24). Thank God that He knows our individual constitutions as our Creator, and pities us like a father pities his children (Ps. 103:13, 14). For each temptation we face with our fallen nature, God provides a gracious means of escape that is uniquely fit for us (I Cor. 10:13). He is the ultimate provider of “personalized medicine” for sin. What a Great Physician!

“Bless the Lord, O my soul, and forget not all his benefits: who forgiveth all thine iniquities; who healeth all thy diseases; who redeemeth thy life from destruction; who crowneth thee with lovingkindness and tender mercies.” Psalm 103:2-4

1 In this context it is important to realize that cancer is not really a single disease, but a spectrum of diseases—each with its own unique causes and features. The National Cancer Institute lists about 180 different cancers known to scientists (, although this is still an underestimate since many of these cancers have distinct subtypes with their own prognoses.

2 Long before the origin of cancer was known, the Greek physician Hippocrates noticed that tumors often formed claw-like tendrils that invaded into normal tissue and described the malignancy as karkinos, the Greek word for “crab.” Rediscovery and translation of Hippocrates’ works at the advent of modern medicine are the basis for our calling the disease by the Latin word “cancer.’