Colson starts this chapter by saying because he has proved that God exists and that the Bible is the word of God, then we can know that there is some ultimate Truth (with a capital tee). He also says that a Christian can know truth, which he defines as "the way things really are", through the Bible and three other ways: Truth in the book of nature, Truth through reason, and Truth through conscience.
Truth in the book of nature is described as look at the beauty in nature, see since it is beautiful there is a God. This of course ignores the ugly side of nature, which I pointed out in chapter 2 when he put forth the same exact argument.
Truth through reason is about reasoning the why's of creation, to Colson. He even makes this beautifully cognitive dissonant statement:
Christianity does not consist of a hidden body of teachings disconnected from everyday realities, nor does it insulate itself in a realm of subjective notions that cannot be disproved.
Colson does not live in reality. That is what that sentence says to me. He lives inside his own head and does not know what reality even looks like. The only reason I will continue on with this book is because my mother asked me to read it. If I was reading this on my own, I would have stopped after reading this sentence. Because it is that divorced from reality.
Gos is the ultimate unfalsifiable entity. No matter what the facts show God could have done it that way. You can't prove that God didn't do it the way science discovered, especially when you posit that God exists outside of our space-time. God has always been and will always be an unreasonable answer, because it is unfalsifiable.
Truth through consciousness. God exists because people know good from evil. Ignoring the fact that the idea of evil has evolved over the last few years and even more so over the last few thousand years (look at slavery, human sacrifice, and equal rights movements), Colson states that there are moral absolutes "written on our heart". Then they must also be written on the hearts of every social animal in the world, because dogs, chimps and monkeys all show signs of knowing good from evil. So how do they fit with the idea of morality coming from God for humans? Colson never mentions them, instead he attacks a straw man of moral relativism. Colson claims that because people think it is wrong to kill Jews or to push an old lady into oncoming traffic, then that means that postmodern relativism is wrong. In fact this proves that morals are relative. In Nazi Germany many people determined that it was okay to kill Jews. Before that many Christians, including Martin Luther (Luther advocated the killing of Jews also), thought that Jews were lesser people. These ideas have changed and evolved, morals have changed over time. Just because a majority of people are against the murder of Jews, does not mean that that has been the case throughout history. Morals are relative to the time, place, and situation.
Colson himself holds a moral view that is slowly going the way of the dodo. He was one of the authors of the Manhattan Declaration. He thinks that allowing same-sex couples to marry is immoral. Currently he is in the majority, but support for same-sex marriage is showing an increase in support over the last 2 decades. It is becoming less immoral overall in America. There could come a time (personally I hope it will be very soon) where it will be immoral to deny this right. Much like when it was finally legal to marry someone of a different race. It seems crazy to us now, but at the time it was hotly debated. Again it was a change in morality.
If I was being more optimistic, I would say that Colson just doesn't know what he is arguing against. I think Colson is knowingly lying for Jesus. It is an ends justify the means tactic. His lies also grow from his self-righteousness too. Fred Clark covered this (here, here, here, and here) so much better than I ever could on his blog, Slacktivist (which I cannot recommend reading enough).
Before I go on, I want to talk about the Code of Hammurabi which Colson mentions here. Hammurabi was a Babylonian King who ruled from 1796 to 1750 BCE. Hammurabi claimed that he talked to the Gods and that they dictated these laws to him on top of a mountain. This is one of the first recorded set of laws in human history (there are a few others from the same area that predate it but not by much). This code predates Mosaic Law. The two sets of laws are very similar and even the story have how they were received are similar. It is almost as if the ancient Hebrews borrowed the story and the laws from the Babylonians.