"The proposition of an established classification of states as slave states and free states, as insisted on by some, and into northern and southern, as maintained by others, seems to me purely imaginary, and of course the supposed equilibrium of those classes a mere conceit"

William H. Seward's quote is a criticism of the idea of classifying states as either slave states or complimentary states, or northern and southern states. He believes that this classification is simply fictional which the expected equilibrium of these classes is a simple conceit. Seward is suggesting that the idea of a balance in between the 2 classes is not based in reality, which the concept of a balance in between the 2 classes is an incorrect idea. He is also implying that the idea of a balance between the two classes is not helpful to either side, as it is not based in reality. Seward's quote is a tip that the concept of a balance between the two classes is not a valid principle, and that it should not be utilized as a basis for decision-making.