"My teacher hath shewn the class how to divide fractions."
"Doing my chores without being asked hath shewn that I can be responsible."
The phrase "hath shewn" isn't one that we typically hear in conversations or see in writing anymore, right? In the passage above, "hath" is a conjugation of the verb "to have" that is not used anymore. For I, we, and ye "they have" would be used. For thou (now we use "they"), the word "hast" would be used. When using the conjugation for he, she, or it, the word "hath" was used. Shewn is a former spelling of the word "shown" that we use today. If Jefferson were to write this passage incorrect contemporary English, instead of "hath shewn", he would write "has shown".