Proof may be provided, but it is faulty proof, pertaining to unaccepted designs. No wonder the OED lists as a further entry under essay 'to assail with words'. Rather than just putting to the proof, the essay attacks, tries, tastes, inquires, experiments. The unattainable luxury of the perfect essay, therefore, is supplemented by a series of pithopractic actions, essaying to zoom in on what they are supposed to be. As Derrida has expounded in Of Grammatology, this idea of the supplement owes to yet another essay, Rousseau's Essay on the Origin of Languages, where supplement is a term denoting the double bind of adding to an already complete entity and thus making good an insufficiency.
Faulty proof is weighed against the question marks of doubt.
It is in this spirit that in 1623, Galileo Galilei published The Assayer, outlining his conception of thought as opposed to the terminology of Aristotelian philosophy. Considering composition and genre, we do indeed tend to focus on form and convention, organisation, structure, architecture, frame, shape, mould, arrangement, scheme, order, plan, outline, design, pattern, fabric, texture, tissue, particle, fraction, element, instalment, bit, slice, scrap, chip, chunk, lump, gobbet - until the thing dissolves and looks like a faulty proof once more. But even the thus accused founder of modern philosophy used the concept of the essay himself, to supply examples and supplement his discourse. This is what Derrida appears to be saying with and beyond Rousseau in Of Grammatology. Discussing the importance of 'articulation' as both word and concept in Rousseau's Essai sur l'origine des langues , Derrida quotes Ferdinand de Saussure to the effect that in Latin, articulus meant a member, part, or subdivision of a sequence.