I. Introduction in Defense of Everything Else

Chesterton outlines his intention for writing Orthodoxy. He had previously denounced other popular belief systems in his book Heretics, and now wanted to explain what he did believe. He says that when he started considering the nature of human life, he found all the conclusions he reached were already Christian doctrine.

II. The Maniac

Chesterton explained that the materialistic worldview is coherent, but very narrow. He argues that the Christian is able to believe in both the supernatural and the natural, but the material list is never allowed "to admit into his spotless machine the slightest speck of spiritualism or miracle." He continues that accepting materialism destroys freedom, because it means the materialist is no longer free to do anything. "[The materialist] must not say to the sinner, 'Go and sin no more,' because the sinner cannot help it."

III. The Suicide of Thought

Chesterton argues the modern world is not evil, it is rather full of virtues gone wrong. He gives the example of the Christian critic Robert Blatchford who says Christianity should become more charitable by eliminating the notion of sin. Chesterton argues this is an example of the virtue of charity going wrong because it is not coupled with the virtue of truth: "Mr. Blatchford attacks Christianity because he is mad on one Christian virtue: the merely mystical and almost irrational virtue of charity. He has a strange idea that he will make it easier to forgive sins by saying that there are no sins to forgive."

Chesterton explains that mere skepticism must eventually defeats itself, by asking the question why is any thought to be reliable, if all thought is just "movements in the brain of a bewildered ape."

IV. The Ethics of Elfland

Chesterton argues the modern world frequently confuses necessary laws of reason and mere associations. "For instance, if the Ugly Sisters are older than Cinderella, it is... NECESSARY and that Cinderella is younger than the Ugly Sisters." Similarly, "you cannot IMAGINE two and one not making three." These cases are to be distinguished from mere patterns, like apples growing on trees. "You can easily imagine trees not growing fruit; you can imagine them growing golden candlesticks, or tigers hanging on by the tail." Chesterton contains fairytales keep this sharp distinction between necessary laws of reason and the science of physical facts, which are not laws of nature. Chesterton explains that he felt the world is full of contingent things they didn't have to be a certain way, while the modern world thinks the world is as it necessarily had to be.

V. The Flag of the World

Chesterton describes his attitude toward the universe as patriotism and irrational optimism. He then explains that this is the only attitude that can actually improve the world. He argued that the man who is most likely to ruin the place. He loves is the man who loves it with a reason. The man who will improve that place is the man who loves it without a reason. If a man loves a particular feature of a place, he might defend that feature at the expense of the place itself. But if he simply loves a place, he is prepared to do anything to elevate it. He then argues this is the attitude of Christianity.

VI. The Paradoxes of Christianity

Chesterton argues that the modern world makes paradoxical critiques of Christianity. They simultaneously attack Christianity as too pessimistic and too optimistic, as too womanly and too anti-woman, as too timid and too violent. He says Christianity is attacked from both sides not because its a mere compromise of two extremes, but rather because it fully embraces paradoxical virtues. It equally embraces the valor of the martyr, and the pacifism of the monk.

VII. The Eternal Revolution

Chesterton argues modern evolutionary thoughts precludes reform. He says all revolution necessitates a fixed vision, and that modern notions of ever-changing ideals immobilize any revolutionary change. He says Christianity maintains this fixed vision modernists lack.

VIII. The Romance of Orthodoxy

Chesterton claims the modern world feels meaningless because there are no rules. Christianity on the other hand, offers adventure within a set of rules. He makes the comparison of children on an island. If the children have walls that protect them from the ocean, they can wrestle and play with each other without fear. However, if those walls disappear, the children will be paralyzed in the middle of the island, afraid they'll fall in.

He writes that modernists who deny the existence of miracles a priori are illiberal in thought. They are not free to consider all possibilities.

IX. Authority and the Adventurer

After explaining the rectitude of the foundation of Christian philosophy for the last few chapters, Chesterton now explains why he doesn't merely keep Christian philosophy and leave Christian dogma. He explains he believes in Christianity because of the evidence and rebuts three common reasons for disbelief. Then, he writes that he believes in Christianity, not because it has told the truth, but because it is a "truth-telling thing", and just as it has taught him before, it will continue to teach him tomorrow.