“He who has a clear idea can also express it clearly.”Georg Christoph Lichtenberg · Caietele de însemnări · 1799 · Caietul K, însemnarea 22
If you can't say it clearly, your idea isn't ready yet — clarity is the test of understanding.
Lichtenberg reverses the usual excuse of people who speak vaguely. Vagueness is not a stylistic flaw but a signal: the idea itself is confused, incomplete, or contradictory. Clear expression is the test of understanding. When someone tries to explain a decision to a friend and keeps stumbling over sentences, they usually discover they do not yet know what they want. Writing simply forces thinking to be finished.
Confusion has a hidden advantage: it is a detector. When you try to say something and feel the sentences jam, that jam shows you exactly where your thinking is still soft. Lichtenberg suggests not pushing past the moment, but using it. Restate until the sentence comes out on its own, simple. For instance, if you cannot tell a colleague in one sentence why a project should be stopped, the real cause may not be the project, but that you have not yet found the main reason. Clarity does not come after thinking; it is thinking, seen from outside. Next step: what do you actually do when the detector goes off and the text refuses to settle.
Why it matters Useful to anyone who writes, teaches, or leads: if a message will not come out clearly, the thinking is unfinished, not just the phrasing.