| canny(adjective, reasonable, keen, sharp, smart) |
| capable(smart, bright, active, wise, brainy) |
| cerebral(adjective, sound, reasonable, sensible, rational) |
| circumspect(sound, reasonable, sensible, reasoning, intellectual) |
| clear-cut(adjective, sound, sensible, rational, intelligent) |
| cognitive(adjective, sound, reasonable, sensible, rational) |
| cognizant(adjective, sound, reasonable, sensible, rational) |
| collected(calm, sound, reasonable, sensible, intellectual) |
| competent(bright, active, wise, sharp-witted, quick-thinking) |
| composed(calm, sound, reasonable, sensible, stable) |
| conscious(adjective, sound, reasonable, sensible, rational) |
| consequent(adjective, good, sound, reasonable, sensible) |
| consistent(adjective, sound, sensible, rational, intelligent) |
| conversant(adjective, reasonable, sympathetic, rational, intelligent) |
| coolheaded(calm, sound, reasonable, sensible, rational) |
| credible(adjective, sound, sensible, rational, intelligent) |
| deductive(sound, reasonable, sensible, reasoning, intellectual) |
| deep(smart, bright, brainy) |
| deliberate(sound, reasonable, sensible, reasoning, intellectual) |
| dependable(calm, sound, reasonable, sensible, proper) |