When communicating with an unknown audience you can't make any assumptions of pre-existing knowledge. Especially if that knowledge is considered essential to the topic at hand. If you do otherwise it will leave the audience confused, or confident but with potential misunderstandings.
If this were in person, he might have been able to ask, "What do you know about the US's method of setting a budget and taxation?" and tailored his response after that. Since it was a letter, greater caution was needed.
Are you offended by the first chapter or two of nearly every programming language book that explains what variables, conditionals, arrays and the like are? If you know it, you can skip it. If you don't, you can read it to have a better foundation for the rest of the text.
If this were in person, he might have been able to ask, "What do you know about the US's method of setting a budget and taxation?" and tailored his response after that. Since it was a letter, greater caution was needed.
Are you offended by the first chapter or two of nearly every programming language book that explains what variables, conditionals, arrays and the like are? If you know it, you can skip it. If you don't, you can read it to have a better foundation for the rest of the text.