After some difference from the official answers on questions 13 and 15 I would like to propose the following change to this question.
Currently the passage reads
Rene Descartes, a 16th century Frenchman often regarded as one of the founders of modern philosophy, penned one of its most famous slogans: “I think, therefore I am.” This statement was the conclusion to an approach of systematic doubt, the goal of which was to arrive at a new foundation for knowledge. He might have been able to doubt all the evidence of his senses, Descartes reasoned, but he could not doubt the proposition that he himself existed to do the doubting. His statement might almost be rephrased as: “I doubt, therefore I am.” Yet despite the fact that philosophers since the early 19th century have made heavy use of this conclusion, Descartes in his own day was most influential as a scientist, not a philosopher.
Throughout 16th century Europe, for example, Descartes was well known for his work in physics, geometry, and physiology, and modern scholars still consider him one of the precursors of the scientific revolution. His attempts to use algebra to solve problems of space and motion essentially created the field of analytic geometry, upon which modern applied mathematics is still largely based. Descartes discovered the law of refraction, which explains why straight objects appear bent when immersed partly in water, and was one of the first to theorize that the workings of human bodies can be studied in similar fashion to the workings of machines. Even his “Discourse on Method,” which contained the famous philosophical statement, was intended merely as the framework within which a collection of essays on optics, meteorology, and geometry was to be understood.
Questions 13 and 15 refer to the organization and purpose of this passage, seeing an argument is key to making a selection that matches the Official Answers.
The argument is most clearly stated in the final sentence of the first paragraph
Yet despite the fact that philosophers since the early 19th century have made heavy use of this conclusion, Descartes in his own day was most influential as a scientist, not a philosopher
This sentence qualifies his influence using the words in his own day
. These words cause confusion. Is the argument, in the following sentences, designed to resolve Descartes as a historical figure from our current perspective, or during his lifetime. Removal of these 4 words would resolve confusion without requiring changes to the answer choices or any other part of the test.
Anyone else thing removal of in his own day
, would improve the clarity of this problem without making it too easy?