The correct answer is 1. John Locke because he is the philosopher who advanced the theory that the mind is a "tabula rasa" (Latin for "blank slate") at birth.
In his work "An Essay Concerning Human Understanding" (1689), Locke proposed that human beings are born without any innate ideas or knowledge. Instead, all knowledge comes from experience, specifically through two sources: sensation (our experiences of the external world through the senses) and reflection (the mind's internal operations and thoughts). According to Locke, the mind is like a blank slate (tabula rasa) at birth, and everything that an individual knows comes from experience after they are born.
The other figures mentioned did not propose this theory:
John Wesley was a theologian and founder of Methodism, not a philosopher of the mind.
Isaac Watts was a theologian and hymn writer.
Denis Diderot was a French philosopher and writer, but he is best known for editing the Encyclopédie and did not propose the "tabula rasa" theory.
Thus, John Locke is the correct answer.