What is instructions?

If one writes logically, he will prove his point. is this sentence correct or contains an unwarranted shift in person?

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were a wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

"she is his achilles' heel" is an example allusion alliteration simile personification