Step 1: Understanding the Task
The task is to rearrange the four parts to form a well-known aphorism about perfection.
Step 2: Finding the Logical Flow
The sentence is built on a contrast structure: "not when X, but when Y".
Part P starts the sentence and introduces the first part of the contrast: "perfection is achieved, not when there".
Part Q completes this first clause (the 'X' part): "...is nothing more to add,". So, the sequence must start with P-Q.
Part R begins the second part of the contrast with the conjunction "but": "but when there is nothing". This is the 'Y' part.
Part S completes the second clause: "...left to take away." This logically follows R.
Step 3: Constructing the Final Sentence
The complete sentence reads: "Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away."
Step 4: Final Answer
The sequence PQRS correctly forms the aphorism. Therefore, option (A) is the correct answer.