Must good philosophers be good writers?

Bryan Magee in Prospect:

I used to encounter more often than I do now the assumption that philosophy is a branch of literature. In fact when I was younger I often met people-intelligent and educated but untrained in philosophy-who thought that a philosopher was somebody giving voice to his attitudes towards things in general, in the same way as an essayist might, or even a poet, but more systematically, and perhaps on a larger scale: less opinionated than the essayist, less emotional than the poet, more rigorous than either, and perhaps more impartial. With the philosopher, as with the other two, the quality of writing was an essential part of what was most important. Just as the essayist and the poet had a distinctive style which was recognisably theirs, and was an integral part of what they were expressing, so did the philosopher. And just as it would be self-evidently nonsense to say of someone that he was a bad writer but a good essayist, or a bad writer but a good poet, so it must surely be nonsense to say of someone that he was a bad writer but a good philosopher.

This attitude is completely mistaken, of course, because it is refuted by some of the greatest philosophers. Aristotle is regarded as one of the greatest philosophers of all time, but all that remains of his work are lecture notes, made either by him or by a pupil. And as we would expect of lecture notes, they are stodgy, bereft of literary merit. But they are wonderful philosophy just the same, and they have made Aristotle one of the key figures of western civilisation. The conventional wisdom has long held that the outstanding philosopher since the ancient Greeks is Immanuel Kant, but I cannot believe that anyone has regarded Kant as a good writer, let alone a great stylist: to anyone who has actually read his work such an idea would be as difficult to understand as some parts of his transcendental deduction of the categories. The founder of modern empiricism and modern liberal political theory, John Locke, is another central figure in western philosophy, but he writes in a way that most people seem to find dull and pedestrian.

More here.