Ian is brilliant and loves his work. During their first encounters, Ian and Charlie clashed: Charlie did not believe in using guns to solve problems and disdained Ian's dispassion about killing. In contrast, Ian thought Charlie's mathematic approach was too academic for real cases, and his scientific viewpoint made his objections to Ian's attitude hypocritical.
Ian is exceptionally talented at his job and finds it fulfilling. Their initial encounters involved a disagreement: Charlie did not think using weapons to solve problems was effective, while Ian found Charlie's mathematical approach too theoretical for real-world scenarios. Additionally, Ian perceived Charlie's scientific viewpoint as making his criticism of Ian's attitude appear hypocritical.