Sine qua non

Without which there is nothing;
indispensable requirement;
something essential;
as, Love is the sine qua non of human existence.

Latin, short for conditio sine qua non, meaning, condition, without which, no. Something not open to negotiation, a take it or leave it proposition.

As in, "links are the sine qua non of everything."

The expression
"It is that city's sine qua non" is often used to convey the specialness of that place; it's uniqueness.

It is more accurately the essence of a place or thing, which is not the same thing at all. The former is the defining characteristic (a landmark perhaps), while the latter is the soul, the heart of a thing.

What is characteristic of a place or thing (what it is associated with) is not necessarily that which makes it wonderful.

La petit prince

A Latin term usen in Roman law. As the other writeups state, the translation means "without which it could not be" or "something that could not have been without". In legal terms it is used when an (careless) action is triggered by an condition. Example: The child could not have fired the pistol and shot the playmate if the father had a gun lock on the gun.

See also: Proximate cause, Causation

In tort law, there are three essential elements to every cause of action: (1) existence of a duty, (2) breach of the duty by the defendant, (3) causation of harm.

Sine qua non¹ or conditio sine qua non is one theory of causation. Basically, the defendant's breach of duty (element (2)) will be considered the conditio sine qua non of the plaintiff's injury if "but for" defendant's act or omission, the harm would not have been sustained. This is what is known as the "cause in fact."

However, sine qua non can be both overinclusive and underinclusive. For example, if A fires a starter pistol, which causes birds in the next county to scatter about madly, eventually running into a small aircraft and causing it to crash, clearly, A's firing of the starter pistol is the conditio sine qua non - if he hadn't spooked the birds by firing the pistol, the birds wouldn't have caused the plane to wreck. However, it does not necessarily seem reasonable to hold people responsible for the remote and unforeseeable consequences of their actions. Thus, in U.S. tort law, the line between causation and dutyis often hazy. This rather poorly delineated blob is known as "legal causation." In order to satisfy the causation requirement, the defendant's wrongful act must not only be the "cause in fact" (conditio sine qua non), but also the legal, "proximate cause."

---

¹ Lat. "without which, not"