The worth of the ideal must be largely determined by the success with which it can in practice be realized. We should abhor the so-called “practical” men whose practicality assumes the shape of that peculiar baseness which finds its expression in disbelief in morality and decency, in disregard of high standards of living and conduct. Such a creature is the worst enemy of the body politic. But only less desirable as a citizen is his nominal opponent and real ally, the man of fantastic vision who makes the impossible better forever the enemy of the possible good.

Theodore Roosevelt (1858-1919) American politician, statesman, conservationist, writer, US President (1901-1909)

Speech (1910-04-23), “Citizenship in a Republic [The Man in the Arena],” Sorbonne, Paris
    (Source)