3 ideas
Tweel learns several English words and follows Jarvis's diagrams of the solar system, yet Jarvis can never learn a single Tweel word, and Tweel's words seem to shift meaning from use to use. The story explains the gap as minds built on different premises rather than a ranking of smart and dumb. An alien mind can be fully capable yet mostly unreadable, because its categories do not map onto ours.
Jarvis and Tweel share only a few words, gestures and diagrams, yet they become loyal allies after each saves the other's life. The story grounds their trust in these rescues, which show intent in action more clearly than their partial language can.
The dream-beast draws prey by projecting an image of what the victim wants, and it shows Jarvis a woman he once knew. Jarvis cannot tell what, if anything, Tweel saw. Tweel saves Jarvis by holding him back and shooting the creature.