Tools for Deeper Thinking
Good writing and good thinking necessarily go hand-in-hand. And learning to write and learning to think deeply similarly go hand-in-hand. The same exercises that teach a student to write well also teach them to think deeply.
The Lost Tools of Writing™, therefore, can be taught in conjunction with history, science, philosophy, humanities, religious studies, music, art, even math, and certainly English. By insisting that students write about what they are learning in their other courses, teachers can employ the exercises in the The Lost Tools of Writing™ to help the students think more deeply about the events, people, and ideas taught in those courses.
In that way The Lost Tools of Writing™ is truly "cross-curricular".