Being rational means exercising good judgment when marshaling evidence and deciding whether a theory or insight is true or just probable. Intelligence usually refers to how fast or how slow it takes someone to understand a theory or insight, but people have blind spots about religion and cannot even grasp certain ideas. This is because religion causes conflict, conflict causes anxiety, and inhibition is a defense mechanism for anxiety. People are inhibited from thinking intelligently and rationally about religion.
I would give Greenblatt a very low score on following test of intelligence and rationality. There are four answers to each question, and the test includes listing the answers from the least rational to the most rational:
What is the relationship between my self and my body?
What caused the universe to begin 13 billion years ago?
What should our goal in life be?
The four solutions to the mind-body problem are 1) dualism, 2) materialism, 3) idealism, and 4) the metaphysical answer. Dualism is the theory that spiritual substances exist. Materialism is the theory that only the body exists and the mind is some kind of illusion or epiphenomena. There is more evidence for materialism than dualism because material substances, unlike spiritual substances, do indeed exist. Idealism is the theory that God gives us the illusion of having bodies so that we can communicate with each other. There is more evidence for idealism than materialism and dualism because we can imagine that our bodies are illusions, but we can't imagine that we don't exist. The metaphysical answer is that the mind-body problem is a mystery and that humans are embodied spirits.
The four answers to the question of what caused the Big Bang are: 1) God did it. 2) An angel did it. 3) The universe is not intelligible. 4) The scientific method will eventually produce an answer. There is no evidence that God caused the universe to begin, other than quotes from the Bible. There is more evidence that an angel did it because an angel would have a motive for doing such a thing. The theory that the universe is not intelligible arises from the observation that animals don't ask questions. Just because a human being asks a question, does not mean there is an answer. No. 4 is the answer judged to be true by many rational people.
The four answers to the question of our purpose in life are: 1) Humans should increase pleasure and decrease suffering. 2) Humans should try for fulfill their potentials. 3) Human life has no meaning or purpose. 4) Humans should serve God in this world in the hope of being with Him in the next. No. 1 conflicts with the great mystery that people who devote themselves to their own happiness tend to be unhappy, and people who devote themselves to the happiness of others tend to be happy. No. 2 ignores the fact that humans can fulfill their potential in different ways. The problem of life consists precisely of deciding how to fulfill our potentials. Saying we should fulfill our potentials or achieve self-realization has no truth content or value at all. No. 3 and No. 4 are the only two answers supported by evidence.
I give myself a score of 100 points: 6 points for each of the 12 answers, 12 points for understanding the mind-body problem, and 16 points for putting the answers in the right order. I estimate Greenblatt's score at only 18 points. He gets no credit for his ideas about the origin of the universe because he doesn't know the difference between God and an angel. He gets no credit for the meaning of life because he assumes there is no evidence for life after death. He only gets points for understanding materialism, dualism, and idealism. He may deserve points for understanding human beings have souls even though he doesn't understand that the human soul is spiritual. Most atheists think the human soul is spiritual by definition and that humans do not have souls. Body (matter) and soul (form) are the metaphysical concepts that explain why humans are equal to each other, but at the same time different from each other.
Greenblatt doesn't realize that not having a meaningful life makes people prone to irrational beliefs. People who don't believe in God believe in anything, it has been said. Examples of irrational beliefs by the likes of Jefferson and Machiavelli are laissez faire capitalism, socialism, nationalism, anti-Semitism, imperialism, and eugenics. These are the beliefs that gave us what Greenblatt calls "modernity." In my opinion, what these beliefs gave us is the atrocities of the French Revolution, the Napoleonic Wars, the Franco-Prussian War, the American Civil War, the First and Second World Wars, and Nazi and Communist genocide.
A number of times, Greenblatt implies that the Catholic Church was against science. He cited the disagreement with Galileo about the heliocentric model in the 17th century, which was invented in the 16th century. In my opinion, the Catholic Church exercised better scientific judgment than Galileo. If the Earth moved around the Sun, the position of the stars would not be fixed. It was only a century later that improvements in telescopes enabled astronomers to observe the motion of stars as our planet revolved around the sun.
It can be argued that modern science began in the 13th century when the Bishop of Paris, acting upon the advise of scientists at the University of Paris, condemned certain propositions by Aristotle because they implied that God was not omnipotent. Faith in God and the belief or hope that the universe is intelligible is what gave mankind ongoing and sustainable scientific achievements. The scientific achievements of the Greek civilization were isolated. Science in all other civilizations was virtually nonexistent because of belief in pantheism and eternal cycles, instead of belief in the immutable and infinite being Christians, Jews, and Muslims call God.