consider, reflect, think
惟 centers on careful mental activity: considering something deeply, reflecting on it, or thinking it over.
惟 combines 忄 (heart/mind) with 隹, which likely contributes the sound. The structure suggests mental activity, fitting the meanings of considering and reflecting.
The heart radical 忄 beside 隹 suggests a mind focused like a bird: carefully considering and reflecting on what it sees.
For イ, imagine you are thinking deeply, and the sound of your own thought is a quiet 'ee' (イ). Picture yourself saying 'ee' as you consider an idea.