Blank (i): ignorant
- Context: The semicolon (;) sets up an explanation for the type of scientist Maxwell considered the "best." The explanation is that they are "not hemmed in" by certain limitations, allowing them to approach problems with an open mind.
- Fit: The scientist is not hemmed in by the past rules and assumptions of the field. A scientist who is free from established limitations or prior knowledge is, in a sense, ignorant of those constraints. This word creates a necessary paradox with "best scientists."

Blank (ii): preconceptions
- Context: The blank describes the constraint that the best scientists are "not hemmed in by". This constraint prevents others from seeing problems clearly.
- Fit: If the scientists are free to approach problems with an open mind, they must be free from preconceptions (an idea or opinion formed before having actual evidence). This directly aligns with the idea of being "not hemmed in."
- Myopia means shortsightedness, which is too literal for a field's ideas.
- Inertia means a tendency to do nothing or remain unchanged (describes a state of being, not a set of ideas).

Blank (iii): empty
- Context: The final blank describes the mind that results from being free of constraints (Blank ii). It is described as a "mind, so to speak," suggesting a straightforward, literal adjective is needed.
- Fit: If the mind is free of preconceptions, it is empty of existing ideas, allowing for genuine novelty. The phrase "so to speak" reinforces that the word is a direct, if somewhat paradoxical, description of a mind ready to receive new information.
- Fertile and rational are positive, but they don't capture the idea of being free from prior data, which is the core logical point of the sentence.

The completed sentence reads:

James Clerk Maxwell once remarked that the best scientists are, in a sense, the ignorant ones; not hemmed in by the preconceptions of their respective fields, they are able to approach problems with an empty mind, so to speak.