Reason Never Begins It

A due recognition of the function of reason should be an enormous help to us all in days when the air is full of fallacies, and when our personal modesty, that becoming respect for other people which is proper to well-ordered natures whether young or old, makes us willing to accept conclusions duly supported by public opinion or by those whose opinions we value. Nevertheless, it is something to recognise that probably no wrong thing has ever been done or said, no crime committed, but has been justified to the perpetrator by arguments coming to him involuntarily and produced with cumulative force by his own reason.
Charlotte Mason, volume 6, page 143

Charles Colson comments on Mark Felt admitting that he was the secret source behind the Watergate reporting:

"Now, I understand why Felt wanted to stop Watergate. In my memoirs published this month, titled THE GOOD LIFE, I recall those moments in the White House when now I realize I should have acted to stop the spreading scandal. One night, when, in my presence, Nixon ordered Halderman to get a team in place to do break-ins, I should have stood up and said, "No, Mr. President, you can't do that." But I rationalized that there was a war going on, friends of mine were POWs, and the Cold War was hanging in the balance. Maybe the president was right; we had to take extreme steps to protect the country. And getting Richard Nixon re-elected was, as I saw it then, the most important thing I could do for my country.

What I now realize today, of course, is that we humans all have an infinite capacity for self-justification. Jeremiah was right: "The heart is deceitful above all things, and desperately wicked: Who can know it?'"
~ Chuck Colson, Breakpoint, 'The Return of Watergate'

"After abundant practice in reasoning and tracing out the reasons of others, whether in fact or fiction, children may readily be brought to the conclusions that reasonable and right are not synonymous terms; that reason is their servant, not their ruler,––one of those servants which help Mansoul in the governance of his kingdom. But no more than appetite, ambition, or the love of ease, is reason to be trusted with the government of a man, much less that of a state; because well-reasoned arguments are brought into play for a wrong course as for a right. He will see that reason works involuntarily; that all the beautiful steps follow one another in his mind without any activity or intention on his own part; but he need never suppose that he was hurried along into evil by thoughts which he could not help, because reason never begins it. It is only when he chooses to think about some course or plan, as Eve standing before the apples, that reason comes into play; so, if he chooses to think about a purpose that is good, many excellent reasons will hurry up to support him; but, alas, if he choose to entertain a wrong notion, he, as it were, rings the bell for reason, which enforces his wrong intention with a score of arguments proving that wrong is right. "

~ Charlotte Mason, Towards a Philosophy of Education, pages 142-3