Evolutionary thinking smashes through the IF-THEN log jam by instead using the IF-AND-ONLY-IF-THEN statement. Here's an example: If and only if it is Friday, then evolutionists play poker. In this example, if we observe evolutionists playing poker then it must be Friday. There is no other possibility. Unlike the IF-THEN statement, the IF-AND-ONLY-IF-THEN statement allows you to establish truths.
Evolutionists have used this powerful technique to establish the truth of evolution. Consider perhaps the most famous phrase in evolution today: "Nothing in biology makes sense except in the light of evolution." This was written by the famous twentieth century evolutionist Theodosius Dobzhansky and the phrase continues to be celebrated by evolutionists today. It is equivalent to claiming that "Everything in biology only makes sense in light of evolution," or in the IF-AND-ONLY-IF-THEN statement format as: "IF-AND-ONLY-IF evolution is true, THEN will we find what we find in biology."
It is all suddenly so simple--of course evolution is true. It is a wonder that creationists ever doubted this obvious truth. From where else can you get that kind of certainty except evolutionary thought?
The power of the IF-AND-ONLY-IF-THEN statement, as you can see, is that it covers the water front. It provides knowledge of all possible explanations. Evolution, and only evolution, can explain biology. No other explanation works.
Philosophers such as Kyle Stanford have worried that science is vulnerable to the problem of unconceived alternatives. How can we really know that no other explanation works? How can we even know what are all the possible alternatives? But as usual philosophers fail to comprehend the power of evolutionary thought.
Evolutionists have powerfully used the IF-AND-ONLY-IF-THEN statement for centuries to prove their ideas. They have provided true-truth like no other tradition in the history of thought. And for that we must thank them gratefully. To fully appreciate the power, and simplicity, of evolutionary thought, here is how the Reverend Jerry Coyne applies this logic to lanugo. Here is the Word of Coyne:
One of my favorite cases of embryological evidence for evolution is the furry human fetus. We are famously known as "naked apes" because, unlike other primates, we don't have a thick coat of hair. But in fact for one brief period we do--as embryos. Around sixth months after conception, we become completely covered with a fine, downy coat of hair called lanugo. Lanugo is usually shed about a month before birth, when it's replaced by the more sparsely distributed hair with which we're born. ... Now, there's no need for a human embryo to have a transitory coat of hair. After all, it's a cozy 98.6 degrees Fahrenheit in the womb. Lanugo can be explained only as a remnant of our primate ancestry: fetal monkeys also develop a coat of hair at about the same stage of development. Their hair, however, doesn't fall out, but hangs on to become the adult coat. And, like humans, fetal whales also have lanugo, a remnant of when their ancestors lived on land. [80:1]
As usual Coyne skillfully presents evolutionary truths with a gentle and loving message. How obvious it now is that lanugo can only be explained by evolution (or in other words, IF-AND-ONLY-IF evolution is true, THEN will we have lanugo). Now you can see why evolution is true.