Cognitive scientist and philosopher Daniel Dennett is one of America's foremost thinkers. In this extract from his new book, he reveals some of the lessons life has taught him

This book. This book looks awesome.

http://www.amazon.com/Intuition-Pumps-Other-Tools-Thinking/dp/0393082067/

How to compose a successful critical commentary:

1. Attempt to re-express your target's position so clearly, vividly and fairly that your target says: "Thanks, I wish I'd thought of putting it that way."

2. List any points of agreement (especially if they are not matters of general or widespread agreement).

3. Mention anything you have learned from your target.

4. Only then are you permitted to say so much as a word of rebuttal or criticism.

The word "surely" is as good as a blinking light locating a weak point in the argument.

Don't waste time on rubbish!

Sturgeon's law is usually expressed thus: 90% of everything is crap. So 90% of experiments in molecular biology, 90% of poetry, 90% of philosophy books, 90% of peer-reviewed articles in mathematics – and so forth – is crap. Is that true? Well, maybe it's an exaggeration, but let's agree that there is a lot of mediocre work done in every field. (Some curmudgeons say it's more like 99%, but let's not get into that game.)

A good moral to draw from this observation is that when you want to criticise a field, a genre, a discipline, an art form …don't waste your time and ours hooting at the crap! Go after the good stuff or leave it alone. This advice is often ignored by ideologues intent on destroying the reputation of analytic philosophy, sociology, cultural anthropology, macroeconomics, plastic surgery, improvisational theatre, television sitcoms, philosophical theology, massage therapy, you name it.

Let's stipulate at the outset that there is a great deal of deplorable, second-rate stuff out there, of all sorts. Now, in order not to waste your time and try our patience, make sure you concentrate on the best stuff you can find, the flagship examples extolled by the leaders of the field, the prize-winning entries, not the dregs. Notice that this is closely related to Rapoport's rules: unless you are a comedian whose main purpose is to make people laugh at ludicrous buffoonery, spare us the caricature.

I have enjoyed http://en.wikipedia.org/wiki/Sturgeon's_Law since I first learned about it researching Science Fiction in high school.

I think Sturgeon's Law is an underestimate. More than 90% of everything is crap.

Beware deepities!

A deepity (a term coined by the daughter of my late friend, computer scientist Joseph Weizenbaum) is a proposition that seems both important and true – and profound – but that achieves this effect by being ambiguous. On one reading, it is manifestly false, but it would be earth-shaking if it were true; on the other reading, it is true but trivial. The unwary listener picks up the glimmer of truth from the second reading, and the devastating importance from the first reading, and thinks, Wow! That's a deepity.

Here is an example (better sit down: this is heavy stuff): Love is just a word.

Oh wow! Cosmic. Mind-blowing, right? Wrong. On one reading, it is manifestly false. I'm not sure what love is – maybe an emotion or emotional attachment, maybe an interpersonal relationship, maybe the highest state a human mind can achieve – but we all know it isn't a word. You can't find love in the dictionary!

We can bring out the other reading by availing ourselves of a convention philosophers care mightily about: when we talk about a word, we put it in quotation marks, thus: "love" is just a word. "Cheeseburger" is just a word. "Word" is just a word. But this isn't fair, you say. Whoever said that love is just a word meant something else, surely. No doubt, but they didn't say it.

Not all deepities are quite so easily analysed. Richard Dawkins recently alerted me to a fine deepity by Rowan Williams, the then archbishop of Canterbury, who described his faith as "a silent waiting on the truth, pure sitting and breathing in the presence of the question mark".

I leave the analysis of this as an exercise for you.

truth - the ultimate deepity?

Pretty much, yes!