Many people hold the belief that it is bad luck to walk under a ladder without understanding its origin in superstition. This superstition arises from early Christian teachings that an object with three points represents the Holy Trinity: God the Father, God the Son, and the Holy Spirit. Not all Christians are Trinitarians; therefore, walking under a ladder, according to origin, would only be bad luck for a Christian who believed.
The early superstitious thought is that walking under a ladder — through the Holy Trinity — expresses disbelief in the trinity and that one is in league with Satan. Performing such an act, especially in early Christian times, could have gotten one labeled as a witch. Thus, the act could be extremely dangerous.
A straight ladder, when leaning against a building, does form a triangle. The top point connects with the building, the building intersecting with the road forms one corner and the bottom of the ladder makes the third corner. Throughout history, the number three has held extreme symbolic power, representing the masculine or, as Carl Jung called it, the animus.
Even though the number three and the trinity are closely combined, use of three to represent symbolic importance dates far prior to Christianity. Though this superstition is tied to Christian beliefs, it is quite possible that earlier beliefs may have held sway prior to the advent of Christianity. Early ladders predate Christianity.
It may be bad luck to walk under a ladder for a variety of more practical concerns. First off, if a person is on the ladder, a walk under it might endanger either person; some ladders are not particularly safe. Second, a ladder up to a roof might suggest people are working on a roof. Walking under the ladder might endanger the person on the ground if things fall off the roof. Even walking near a site where people are working above is somewhat fraught with danger. People can and have been injured by things dropping from overhead.
Though Christianity claims the superstitious origins that to walk under a ladder is bad luck, truly good sense makes it a dangerous practice. It could be supposed by the most superstitious that those who perform this action are encouraging bad luck. Bad luck might come in the form of having things dropped on one’s head. However, no one has said much about the bad luck of being knocked off a ladder if a person jostles it while walking under it. This is one superstition that probably should be observed, not so much for its religious origins but for its good sense value.