Use resolution to prove that the following logical argument, devised by Lewis Carroll, is valid: No shark ever doubts that it is well-fitted out A fish, that cannot dance a minute, is contemptible No fish is quite certain that it is well-fitted out, unless it has three rows of teeth All fishes, except sharks, are kind to children No heavy fish can dance the minuet A fish with three rows of teeth is not to be despised Conclusion: No heavy fish is unkind to children.