‘Man makes plans,’ goes the Yiddish proverb, ‘and God laughs.’
‘To draw up in advance an exact and detailed plan is to deprive our mind of the pleasures of the encounter and the novelty that comes from executing he work. It is to make the execution insipid for us and consequently impossible in works that depend on enthusiasm and imagination. Such a plan is itself a half-work. It must be left imperfect if we want to please ourselves. We must say it cannot be finished. In fact it must not be, for a very good reason: it is impossible. We can, however, draw up such plans for works whose execution and accomplishment are a mechanical thing, a thing that depends above all on the hand. This is suitable and even useful for painters, for sculptors. Their senses, with each stroke of the brush or chisel, will find this novelty that did not exist for heir minds. Forms and colours which the imagination cannot represent to us as perfectly as the eye can, will offer the artist a horde of these encounters which are indispensable to giving genius pleasure in work. But the orator, the poet, nd the philosopher will not find he same encouragement in writing down what they have already thought. Everything is one for them. Because the words they use have beauty only for the mind and, having been spoken in their head in the same way they are written on the page, the mind no longer has anything to discover in what it wants to say. A plan however is necessary, but a plan that is vague, that has not been pinned down. We must above all have a notion of the beginning, the end, and the middle of our work. That is to say, we must choose its pitch and range, its pauses, and its objectives. The first word must give the colour, the beginning determines the tone; the middle rules the measure, the time, the space, the proportions.’ (Joseph Joubert, 1798, The Notebooks)
‘The power of a country road is different when one is walking along it from when one is flying over it by airplane. In the same way, the power of a text is different when it is read from when it is copied out. The airplane passenger sees only how the road pushes through the landscape, how it unfolds according to the same laws as the terrain surrounding it. Only he who walks the road on foot learns of the power it commands, and of how, from the very scenery that for the flier is only the unfurled plain, it calls forth distances, belvederes, clearings, prospects at each of its turns like a commander deploying soldiers at a front. Only the copied text thus commands the soul of him who is occupied with it, whereas the mere reader never discovers the new aspects of his inner self that are opened by the text, that road cut through the interior jungle forever closing behind it: because the reader follows the movement of his mind in the free flight of day-dreaming, whereas the copier submits it to command. The Chinese practice of copying books was thus an incomparable guarantee of literary culture, and the transcript a key to China’s enigmas.’ (Walter Benjamin, One Way Street, 1925-26: Chinese Curios)
I'm not sure I agree wholly with Joubert that the work of poets, orators and philosophers is qualitatively different to that of painters or sculptors, so that the role of planning is different. From a craft perspective, all planning is to some degree provisional, hence the truth of his aphorism: 'A plan is however necessary, but a plan that is vague, that has not been pinned down.' Joubert's view is that 'sticking to the plan' reduces the possibility of surprise and pleasure in the work, but Benjamin says something stronger: that over-reliance on planning results in the shutting off of possibilities, the denial of perspectives. Over-dependence on planning suits those who want to avoid surprises, who wish to control, and those who are afraid of freedom. In some sad cases it is all of these things.
Perhaps also relevant here is Andrew Lang's remark, which was actually about statistics rather than planning: 'He uses planning as a drunk man uses lamp-posts: for support rather than illumination'.