THE ESSENCE OF TRUTH
Within the realm of the visible, brightness and darkness are not at the same level as colour and brilliance but possess a priority: they are the conditions of the possibility of experiencing the visible in the narrower sense.
But do we thereby know what brightness, light, and darkness are? Brightness and darkness are first and originary; they cannot be explained in terms of anything else. But we do not thereby come to a conception of the essential nature of brightness and darkness. Brightness and darkness are visible, are seen 'in the first place'. But how is what is visible to be defined? For colour is also something visible. So when we refer to visibility, the visible as such is not yet characterized. We must ask what brightness and darkness are in themselves. What does brightness mean and what does it accomplish?
'Brightness' [Helle] comes from 'reverberate' or 'echo' [hallen] and is originally a character of tone or sound, that is, the opposite of 'dull'. Brightness, therefore, is not at all originally a character of the visible, but was transferred over in language to the visible, to the field where light plays a role. So we speak of a 'bright sunny day'. But such linguistic transferences from the realm of the audible to that of the visible are never accidental, and generally indicate an early power and wisdom of language - although we freely admit that we have only a very inadequate and superficial knowledge of the essence of language. If the meaning of 'bright' is transferred to the visible and made equivalent to 'lit up', 'brightness' made equivalent to 'light', this can only happen on the basis of an essential kinship between the two phenomena, such that brightness as reverberation has something essential in common with light as illumination. The bright tone or sound, which is further intensified in shrillness (e.g. the nightingale) is what penetrates: it not only spreads itself out, but it forces itself through. What is dull or sluggish stays back as it were, is not able to force itself through. Brightness has the character of going-through. The same thing is shown in a different way with light and the 'light of day'. Light also has the character of going-through, and it is this character, as distinct from the staying-back of darkness, which allows the meaning of 'brightness' to be transferred from the audible to the visible. Brightness is that through which we see. More precisely, light is not only what penetrates through, but is what permits penetration, namely in seeing and viewing. Light is the transparent [das Durchsichtige] that spreads out, opens, lets-through. The essence of light and brightness is to be transparent.
But this characterization, it immediately emerges, is insufficient. It is