All through his life, he swung between the ridiculous and the sublime,

At once he became an enigma. One side or the other of his nature was perfectly comprehensible; but both sides together were bewildering.

Was there a reason behind it? There would be no point in asking Zaphod, he never appeared to have a reason for anything he did at all: he had turned unfathomability into an art form. He attacked everything in life with a mixture of extraordinary genius and naive incompetence and it was often difficult to tell which was which.

Was he smart? No, not exceptionally. Instead, he was a genius.

His Ignorance was as remarkable as his knowledge.

Ordinary he was insane, But he had lucid moments when he was merely Stupid.

He was a dreamer, a thinker, a speculative philosopher... or, as his wife would have it, an idiot.

On the one hand they regarded him as a man of wit and sense, and on the other he seemed to them a maundering blockhead, and they could not make up their minds whereabouts between wisdom and folly they ought to place him.

Anyone moderately familiar with the rigours of composition will not need to be told the story in detail; how he wrote and it seemed good; read and it seemed vile; corrected and tore up; cut out; put in; was in ecstasy; in despair; had his good nights and bad mornings; snatched at ideas and lost them; saw his book plain before him and it vanished; acted people's parts as he ate; mouthed them as he walked; now cried; now laughed; vacillated between this style and that; now preferred the heroic and pompous; next the plain and simple; now the vales of Tempe; then the fields of Kent or Cornwall; and could not decide whether he was the divinest genius or the greatest fool in the world.

Because of the self-confidence with which he had spoken, no one could tell whether what he said was very clever or very stupid.

I found him well educated, with unusual powers of mind, but infected with misanthropy, and subject to perverse moods of alternate enthusiasm and melancholy.

Was he smart? No, not exceptionally. Instead, he was a genius. His imaginative leaps were instinctive,
unexpected, and at times magical. He was, indeed, an example of what the mathematician Mark Kac called a magician genius, someone whose insights come out of the blue and require intuition more than mere mental processing power. Like a pathfinder, he could absorb information, sniff the winds, and sense what lay ahead.

James Joyce seemed like the most arrogant man who ever lived, had both his eyes wide open and great faculty of speech, but what he say, I knew not what.

A man who has the inventive genius can't control it exactly as he wishes. Its working depends in great measure on inspiration — on a momentary suggestion — and it is almost impossible to tell beforehand at what moment it will come.