In the “The physicist as novelist” Alan Lightman explained why topic sentence is central to expository writing. He started by explaining why novelist avoids naming things
By defining ideas precisely, as science does, fiction would deny its readers freedom of interpretation.
I'll give another illustration of the difference between naming and not naming. Let me represent science by expository writing. Like science, a piece of expository writing takes a reductionist and reasoned approach to the world. You have a position or argument, you structure this argument in logical steps, amassing facts and evidence to convince your reader of each assertion. We all learn that in expository writing it is useful to begin each paragraph with a topic sentence. A topic sentence, in effect, states the idea of the paragraph at the outset. You thus begin by telling your reader what he or she is going to learn in the paragraph and how to organize his or her thoughts so as to gain as ordered and structured an understanding as possible.
But in fiction, a topic sentence is usually fatal, because the power of fiction is emotional and sensual. You want your reader to feel what you're saying, to smell it and hear it, to be part of the scene you are creating. You want your reader to be blind-sided, to let go and be carried off to a magical place. Every reader will travel differently, depending on his or her own experiences of life. With a topic sentence, you don't leave room for your reader's own imagination and creativity to be engaged as the paragraph unfolds. The difference can be stated in terms of the body. In expository writing, you want to get to your reader's brain. In creative writing, you want to bypass the brain and go straight for the stomach or the heart.
A 1999 non-technical essay on the chances of a vaccine for AIDs: David Baltimore explains the challenge posed by HIV to the immune system. Look for the topic sentences.
Why can't our immune system control H.I.V.? I doubt that we have all the answers, but we do know some key facts. To understand the situation, we need to realize that the immune system controls viruses in two distinct ways -- by producing antibodies and by programming cells called cytotoxic T lymphocytes.
Let's consider antibodies first. Antibodies were discovered in the
early part of this century and are now well understood. They are proteins
that can bind specifically to viruses and interfere with the viruses'
ability to infect the body's cells. They neutralize a virus's ability
Here for clarity I start a new paragraph but Baltimore didn't.
When people are infected by H.I.V., they produce lots of antibodies. However, this virus has found a way to keep the antibodies from doing their job: It does that partly by coating its proteins with sugar, which keeps antibodies from binding to them. That leaves only a little region of H.I.V. open to attack by antibodies, making it a difficult target to neutralize. In addition, the virus is able to change its structure so rapidly that the immune system cannot keep up with it. Antibodies are the first line of defense against most viruses, and H.I.V. has breached that line.
The immune system's other line of defense is cytotoxic T lymphocytes. Scientists discovered those cells only in the 1960s, and their action is so subtle that we still have many unanswered questions about them. However, we know that C.T.L.'s can completely control the growth of certain viruses in animals. We also know that in monkeys, C.T.L.'s can partly control simian immunodeficiency virus (S.I.V.) — a virus analogous to the H.I.V. of humans. As shown recently by scientists in the laboratories of Norman Letvin at Harvard and David Ho at the Aaron Diamond AIDS Research Center in New York City, if most C.T.L.'s in an infected monkey are killed, the concentration of S.I.V. increases 10 to 1,000 times. We believe that C.T.L.'s limit H.I.V. in humans just as they do S.I.V. in monkeys. However, even though they are effective in humans, C.T.L.'s by themselves clearly cannot totally control H.I.V. in most people.
The task of making an AIDS vaccine is evident: Such a vaccine must stimulate the immune system to produce both antibodies and C.T.L.'s, preferably ones that are more effective than those created naturally when someone is infected with H.I.V. That is a tall order.
Where are the topic sentences? How good are they?
At the end of the article, Baltimore notes that the President Clinton in 1997 gave medical research a decade to develop an AID vacine. It has been 13 years, and we don't have a vacine. Using Google and the key words — antibodies and CTL — I did a targeted search. Quickly I learned CTLs are still in the lab. But there had been more progress with antibodies. Some were recovered from a person who nearly survived HIV. Two sets blocked proteins on HIV surface that virus normally uses to access healthy cells. This key feature, constant across most strains of virus, binds to entry point (CD4 receptor). Antibodies covers this region, prevent action of CD4 and entry into healty cell. Of course, there is still more work to do, but recent work is promising.
1. Which has topic sentences? Are they clear?
2. Does material following topic sentence support it with specifics?
3. In speaking even more than writing, repetition can used effectively.
4. There two cardinal rules of exposition that we haven't stressed in concentrating on promoting topic sentences. But why not here?
How did the two speakers do? How might these rules apply to your talks? In judging any text or talk, don't ask who you like or would vote for. Ask instead who made sense
President Bush, in Columbia, Mo.:
"Our strategy is succeeding. Four years ago Afghanistan was the home base of Al Qaeda, Pakistan was a transit point for terrorist groups, Saudi was fertile ground for terrorist fund-raising, Libya was secretly pursuing nuclear weapons, Iraq was a gathering threat, and Al Qaeda was largely unchallenged as it planned attack.
Because we acted, the government of a free Afghanistan is fighting terror, Pakistan is capturing terrorist leaders, Saudi Arabia is making raids and arrests, Libya is dismantling its weapons programs, the army of a free Iraq is fighting for freedom and more than three-quarters of Al Qaeda's members and associates have been brought to justice. We have led, many have joined, and America and the world are safer. ...
We are also serving a vital and historic cause that will make our country safer. Free societies in the Middle East will be hopeful societies which no longer feed resentment and breed violence for export. Free governments in the Middle East will fight terrorists instead of harboring them, and that makes America more secure and the world more peaceful.
So our mission in Afghanistan and Iraq is clear. We'll help new leaders train their armies. We want Iraqis and Afghan citizens doing the hard work of defending freedom. We'll help them through their elections. We'll move - we'll get them on the path of stability and democracy as quickly as possible, and then our troops will return home with the honor they have earned."
Senator John Kerry, in Greensboro, N.C.:
Right now as we sit here, your tax dollars are being used today, yesterday, all last year, tomorrow, your tax dollars are actually being used to reward the company that takes the jobs overseas.
That’s bad enough, but you know there’s something worse, don’t you? It gets worse than that in terms of choices. Today the tax code actually does something that’s right. It actually gives tax breaks to companies that export American products, not jobs, and if you sell more products overseas, and you create more jobs here at home, then those companies get lower taxes so they can grow and hire more people.
Sounds like a pretty good idea, right? Well, George Bush doesn’t think so. He’s wrong again. He wants to end that tax cut, a good incentive that helps the U.S. companies make the jobs here, and he wants — those companies are going to see their taxes raised, and he’s going to take the money from that and give the money to those companies getting a reward for taking the jobs overseas, which will actually encourage more companies to go overseas.