in reason

Synonyms
1. purpose, end, aim, object, objective. Reason, cause, motive are terms for a circumstance (or circumstances) which brings about or explains certain results. A reason is an explanation of a situation or circumstance which made certain results seem possible or appropriate: The reason for the robbery was the victim's display of his money. The cause is the way in which the circumstances produce the effect, that is, make a specific action seem necessary or desirable: The cause was the robber's extreme need of money. A motive is the hope, desire, or other force which starts the action (or an action) in an attempt to produce specific results: The motive was to get money to buy food for his family. 2. excuse, rationalization. 3. understanding, intellect, mind, intelligence. 10. persuade.

Usage note
The construction reason is because is criticized in a number of usage guides: The reason for the long delays was because the costs greatly exceeded the original estimates. One objection to this construction is based on its redundancy: the word because (literally, by cause) contains within it the meaning of reason; thus saying the reason is because is like saying “The cause is by cause,” which would never be said. A second objection is based on the claim that because can introduce only adverbial clauses and that reason is requires completion by a noun clause. Critics would substitute that for because in the offending construction: The reason for the long delays in completing the project was that the costs. … Although the objections described here are frequently raised, reason is because is still common in almost all levels of speech and occurs often in edited writing as well.
A similar charge of redundancy is made against the reason why, which is also a well-established idiom: The reason why the bill failed to pass was the defection of three key senators.