As told to THINK editor Meredith Bennett-Smith; edited for clarity.

When I say that I think President Donald Trump is unfit for office, I want to be precise. I'm keen to distinguish what I mean from stuff I've read earlier this year — the notion that he might be medically unfit or in cognitive decline or have early Alzheimer's. I saw no evidence of that. I found him, as I say in the book, to be of above average intelligence and able to follow conversations. I'm not an expert, but I didn't see any evidence that he's medically or physically unfit for office.

But what did strike me, as I thought about my encounters with him, is that he was somebody without the normal external reference points that a leader has to have. Leaders make hard decisions by drawing upon external reference points, usually a combination of things. Some draw on religious traditions, some draw on logic or philosophy, some on history, some on tradition. Trump’s only reference point appeared to be internal; He is driven by what decision, what course of action will get him the affirmation he so craves. In fact, I've never actually seen in an adult more craving for affirmation.

President Trump’s only reference point appeared to be internal. In fact, I've never actually seen in an adult more craving for affirmation.

Anyone who sees moral equivalence in Charlottesville, who speaks about and treats women like pieces of meat, who lies constantly — about small things, big things, medium-sized things — and who insists that everybody else must believe his lies, has no ethical bearings. Together, these various observations led me to a judgment that I never thought I would actually reach about a president.

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So what do we do now? The impeachment process is one laid out in our Constitution, and it's one that should be driven entirely by the law and the facts. It involves two different branches of government. I don't know where that'll go, but it should be allowed to work as it's designed in the Constitution.

I understand some people want to get him out of office right now. I have heard a lot of this. And my response is, again, that we have a process. It is predicated upon high crimes and misdemeanors, and there's a carefully designed and rarely invoked process to do that. And maybe that'll be appropriate after the special prosecutors finish.

Shaking hands with Trump during an Inaugural Law Enforcement Officers and First Responders Reception in the Blue Room of the White House in Washington in 2017. Bloomberg via Getty Images file

And yet, in some ways I worry that impeachment or the removal of Trump from office would deprive this country of something it desperately needs, which is a point of clarity and inflection. Americans need to stand up and realize that a group of things are much more important than our policy positions. We can have ferocious disagreements about all kinds of issues, but we shouldn't have any disagreement about what is at the core of America, which is a common set of values.

I thought that at the heart of the definition of a conservative was the notion that character matters, and that values matter. I thought that's what it meant to be a conservative. In some ways, Republicans are the most important audience for my book, because I'm ashamed of the way the Republican Party has conducted itself. Republicans know better.

In some ways, Republicans are the most important audience for my book, because I'm ashamed of the way the Republican Party has conducted itself. Republicans know better.

But Americans of all political persuasions need to stand up and participate in the process, our democracy. Because a lot of people voted for Donald Trump, and a lot of people didn't. But also a lot of people didn't vote at all. A huge number of Americans didn't vote. That has to stop.

This is why I think hoping for impeachment is not the answer: Americans need to make sure they get involved now. They need to participate in this democracy, and not become numb to the behavior of our president. I worry that even people who strongly oppose him are becoming immune. They wake up and shrug off a tweet where he's calling for the imprisonment of a private citizen. It’s so outrageous, it's so not normal that we actually allow it to become part of the background noise.

But it’s not normal. I never expected to be in this position. I thought very much I was going to be serving the rest of my six years as FBI director. I believed it would be a nightmare because of the nature of Trump's leadership, but that actually redoubled my sense that I had to stay and protect the institution of the FBI. Plus, I thought there was no way I was going to get fired.

Those still working in Washington and in Trump’s Cabinet have hard choices to make. Each person has to weigh their commitment to the country against the damage that will come to them. I believe that working for Donald Trump, especially closely, damages everybody. And all of us have to decide individually: How much stain can I tolerate in service to my country? And then obviously, there’s the concern that working for him may enable him in some way.

I believe that working for Donald Trump, especially closely, damages everybody. And all of us have to decide individually: How much stain can I tolerate in service to the country?

Trump may not change completely, but there is opportunity for change at the margins. And that's something that all of us can try and help accomplish. He’s a smart person. He's deeply self-interested, and as he comes to understand that you can't do whatever you want as president of the United States, hopefully he also learns there are things the Republicans will not tolerate. And if Republicans do believe that values matter, it's time for them to stand up and put an ethical fence around him in a way that will protect the country.

Ultimately, I hope people will read my book before drawing conclusions about it, or about me. I have heard people say that some of the details I include are beneath me. I would disagree — I offer a lot of details in the book about people I loved as well. I'm not trying to be one way or the other. I'm trying to tell the truth, including about myself.

And as for Trump, if he reads my book I would hope that he would recognize something similar. The truth still matters in America, and that as the leader of this nation he should be always working to hold himself accountable to this idea. Of course, there’s almost no chance that he will read it. And I would be stunned if he takes a lesson from it.

James B. Comey was director of the Federal Bureau of Investigation from 2013 to 2017. He previously served in a variety of government positions including U.S. attorney for the New York Southern District and deputy attorney general, the second-highest official in the Department of Justice. His new book, "A Higher Loyalty," was published by Macmillan on April 17.