The phrase "All Intents and Purposes" finds its origin in the legal language, used in the court cases in the 1500s in England. The initial phrase may have been “to all intents, constructions and purposes”. The phrase for “All Intents and Purposes” is used in a modern scenario in situations where one wants to mean ‘practically speaking’ as in “The class was over for all intents and purposes but the students lingered in the classroom.
"All Intents and Purposes" means in every respect or every practical sense or for every functional purpose. The phrase to all intents and purposes is basically an adverb used in a context like-“to all intents and purposes the theatre is closed”, “The contract is for all intents and purposes not valid anymore. Don’t confuse it with the phrase “to all extent and purpose” which would mean when something remains correct or the same in every scenario, or viewed from any angle.
"All Intents and Purposes" would mean in all the important ways possible, when a professor says to his student: This article is, for all intents and purposes, a plagiarism. I expect better from you.” To "all intents and purposes" would mean virtually, really or in essence when someone says “The old man was impoverished to all intents and purpose”. The widely used synonyms for the phrase "All Intents and Purposes" would be in all applications, really, essentially, design, intention, end, for all practical purposes.
The phrase "All Intents and Purposes" often poses problems as it is often misquoted and results in several malapropisms. For example a common variation would be “for all intensive purposes” which may mean nothing similar to the original phrase. Modern dictionaries sport the phrase “for all intensive purposes” to mean the same as the expression "All Intents and Purposes". The word intense suggests a degree of intensity and is thus incorrectly used in the phrase. Another misquote of the phrase "All Intents and Purposes" is in the use of “for all intense and purposes” or “for all intense purposes”. The meaning of this phrase is again opposed to the original phrase.
The phrase “All intents and purposes” may seem absurd at the outset as it contains two words-“intents and purposes” which may mean almost the same. There is no doubt that the phrase can be used in a number of ways and situations in English, but is somewhat redundant in modern usage. The usage of the phrase “all intents and purposes” may at the most add color to the language like any other phrase or idiom, when used in speaking or writing.