___ al-Haytham, medieval mathematician called “the father of modern optics”

As a detective, my first course of action when encountering a crossword clue is always to break it down word by word, analyzing its possible meanings, and looking for any potential connections between them. In this case, I first focused on the name “al-Haytham,” recognizing it as an Arabic surname frequently associated with scientific scholarship. Next, I considered the descriptor “medieval mathematician,” which suggested that the individual in question was likely a scholar from the Islamic Golden Age, a period known for significant advancements in mathematics and optics. Lastly, I turned my attention to the missing word, recognizing that it needed to be a three-letter word starting with “I” that could refer to a name or title.

Immediately, I realized that the missing word could potentially be ‘IBN,’ a common Arabic prefix meaning “son of.” Given the context of the clue, it made sense that the individual the crossword was referring to would have an Arabic name. Additionally, Ibn al-Haytham was indeed a renowned medieval mathematician and scientist who made significant contributions to the field of optics. Therefore, I confidently filled in the missing word with “IBN,” secure in the knowledge that my careful analysis of the clue had led me to the correct solution.