In what is found the greatness of man? In his understanding? That would leave the difference between man and beast to be a matter of degree. In fact, that would leave beast as our superior; his intellect is perfectly suited to his needs. The path to obtain them - or the cruel reality of his inability - is always clear.
Unique to man is not-understanding - the ability to recognize a vastness which is not understood, and to be inspired by that awareness. The beast lives in his world, which consists entirely of what he perceives. Only man loses himself in the stars.
Once, in reply to a question asked by my revered grandfather, the Rebbe [Maharash], when he was about seven years old, [his father] the Tzemach Tzedek said: “[It is written that] ‘G‑d made man upright.’ The unique superiority of man that G‑d showed him in His kindness by making him walk upright lies in this — that even though he treads upon the earth, he sees the heavens. A four-legged creature, by contrast, sees only the earth.” Source - Hayom Yom