Plant the good seeds of righteousness, and you will harvest a crop of love. [Hosea 10:12 (NLT)]
In a nutshell, compound interest is getting interest on interest; when it’s on money you have, your investment keeps growing. When it’s on money you owe, however, you pay interest on your interest and end up deeper in debt. The economics lesson is because of C.S. Lewis’s words that “Good and evil both increase at compound interest.” While Lewis then switches metaphors from the bank to the battlefield, Scripture often uses the metaphor of sowing and reaping for the same concept of the exponential growth of both good and evil.
After planting just one sunflower, for example, we’d get between 1,000 and 1,400 seeds per head. If each of those seeds were planted, we’d have between one and 1.96 million sunflower seeds the next year and, if we planted those, we’d have between one and 2.7 billion sunflower seeds the third year. If those were perennial sunflowers, we’d also get seeds from the previous years’ plants! Like compound interest, that’s exponential growth (which is what happens with good thoughts and actions).
Of course, if just one Canada thistle seed got planted in that field of sunflowers, it could produce as many as 5,300 seeds that first season! Those thistle seeds would get dispersed by the wind and sow themselves far and wide. Should those seeds take root, more than 28 million new thistle seeds could be blowing through our fields the second year, with the potential of more than 148 billion seeds the following one. With that kind of exponential growth, our beautiful field of sunflowers soon would be overrun by thistles. Worse, those thistles would have spread into our neighbors’ fields. Noxious weeds and evil have a way of doing that!
Since thistles also sprout from their roots, that one thistle could grow into a six-foot thistle patch in a year. Turning to Lewis’ battle metaphor, that loss of acreage is similar to a general losing an asset like a seaport. Worse, because thistle seeds can remain viable in the soil for up to twenty years, like an enemy who’s patiently waited for our troops to get careless, those weeds can spring up years later when least expected. Just as the farmer has to be vigilant in his fight to keep thistles from overtaking his fields, the general must keep his troops battle-ready.
The subject, however, is neither military science nor agriculture; it’s spiritual warfare. Generals and farmers don’t want to cede territory to their enemies, nor do we. Our battle isn’t against armed troops or thistles; it’s against evil. Rather than tanks or herbicides, we need obedience to God’s word and the power of the Holy Spirit! When we act as would Jesus, by sowing seeds of goodness, it’s like planting another sunflower in the garden of life. But, every time we follow our own sinful desires, instead of losing a field to thistles, we lose ground to Satan. In our every act, either a seed of good or evil is planted and, like a thistle seed, any seed of evil is one seed too many!
Good and evil both increase at compound interest. That is why the little decisions you and I make every day are of such infinite importance. The smallest good act today is the capture of a strategic point from which, a few months later, you may be able to go on to victories you never dreamed of. An apparently trivial indulgence in lust or anger today is the loss of a ridge or railway line or bridgehead from which the enemy may launch an attack otherwise impossible. [From “Mere Christianity” by C.S. Lewis]