It means, allegedly, a congruence between appearance and reality: “being exactly what is claimed.” I would not be so to my nature were I not to reach, reflexively, however dull and pedantic may be the impulse, for the etymology: it comes through French, from the Medieval Latin authenticus, which in turn comes from Greek αὐθεντικός “original, genuine, principal.” There is a sense in which the “authentic” is that which is unique, otherwise singular, inimitable in that imitation would create a copy that by its nature would be invalid.
Αὐθεντικός comes from αὐθέντης, that is, “one acting on one's own authority.” Three definitions for this origin-word are given: the first, a perpetrator of any act, in the sense of a murderer; second, a suicide; third, an absolute ruler, an autocrat. There is an element of taking the most decisive, being fatal, actions into one’s hands. This metallic core of violence seems to reflect back the seriousness with which authenticity is invoked. With this term the stakes feel inherently high.
Aὐθέντης, in turn, is sourced from αὐτο- (“self”), combined with ἕντης, which comes from Proto-Indo-European *senh₁- (“to prepare, work on, succeed”) and the Greek -της (a masculine agentive suffix)— a self-accomplishing man. Rattling around in here is the dirt that may become self-actualization in a later age. From this same source, ἀνύω (“I effect, accomplish”) and συνέντης (“helper, accomplice) also derive.
There is a distinction to be drawn between “authentic,” “genuine,” and “true.” The first, implies that the reality of the thing is not fictitious; the second, that the presented author is the true author; the third, that of being solid, accurate, and in good faith (“truth” itself being a funny word that becomes loyalty, faith, covenant, honor, pledge, and fidelity the deeper one digs into it).
There is frequently a conflation between the “authentic” and the “trustworthy.” Because the authentic is that which is taken to be what it appears, one assumes one gets what one sees, and that there will be no gap between appearing, seeming, and being. The taking of one thing with the confidence one will receive what one sees is a particularly economic form of trust.
The first and most basic element of divination, discernment, and vision resides in the analogic principle— that is, “As above, so below.” The authentic might be said to be that whose appearances can be taken as evidence of one’s being; that whatever figment of the “below,” or visible, that one glimpses, it is a true and representative signifier of what exists “above,” or invisibly. It is therefore often taken as a signal that one might take what one sees at face value and need not take any further observation; that one might race across the extrapolative1 bridge without plunging into a tasteless abyss.
More modern valences of “authentic” carry implications that one stands beside or behind what one is purporting, or doing; that is, imply a kind of ownership of appearance. As there is little that most modern minds fear more than taking responsibility, the term also carries a vulnerable tinge, a pitiable credulousness, a species of spiritual liability latent in the nerve it takes to “be oneself” when appearances will be taken for truth.
Ultimately it is very difficult to be other than what one is. One can do all kinds of things that one is not suited to, that are ingenuine to one’s desires, yet how one goes about it all will give one away. Acting “inauthentically,” one’s misery or misfit will find one out; acting authentically, the appearance is the truth. To live is a gift, and it is to be given away.
One can only be what one is, and sometimes what one imagines. Imagination conjures a vision, which creates a possibility, which in turn creates an obligation, which in turn creates responsibility, which when left undischarged generates the pressure that is sometimes called fate. To imagine without action is how some kinds of curses begin.
“To extrapolate” being a word derived for use in reference to astronomy and the extraction of inferences from data, borrowing from “to interpolate,” which is “to alter by inserting new material”; interpolate being a combination of the Latin words for “polishing” and “between,” carrying connotations of cloth.