Ab Initio

Latin: from the beginning

In legal contexts, it is often used to indicate that something was valid or invalid from the start. For example, a contract that is "void ab initio" is considered invalid from the moment it was created, rather than from the time a court addressed the issue.

Imagine you're playing a game, and someone breaks a very important rule right at the start, but it wasn't discovered until later. They got an unfair advantage for the entire time, so by the time it's discovered, there may be a big difference between throwing out only the last move vs throwing out the whole game. If the game is stopped and declared invalid from that first moment, it's like the whole game never really counted — it's invalid ab initio.

In contract law, ab initio is significant because it determines whether a contract is legally binding from the outset. If a contract is void ab initio, it is treated as though it never existed, and neither party can enforce it.

If a judge rules that it is void ab initio, it means it was never legally valid from the start — not just from when a judge says so, but as if it never existed at all. This is different from a "voidable" contract, which is valid (or treated as valid) until one party challenges its validity.

For example:

• A marriage is void ab initio if one of them was already married (bigamy).
• A contract signed under fraud might be void from the beginning.

It’s different from something that becomes invalid later — ab initio means it was wrong from day one.

It’s also used in science and computing (like ab initio calculations in physics), where results are based on basic principles, not guesses or past data.