In fact if the mind is disciplined to separate pure thinking from mere imagining, the infinite is not difficult to think. Spinoza saw and expressed this by making a distinction between “infinitum actu (or rationis),” and “infinitum imaginationis,” and his first and second axioms are the immediate results of thought elevated to this clearness. This distinction and his “_omnis determinatio est negatio_,” together with the development of the third stage of thinking (according to reason), “_sub quadam specie æternitatis_,”—these distinctions are the priceless legacy of the clearest-minded thinker of modern times; and it behooves the critic of “human knowing” to consider well the results that the “human mind” has produced through those great masters—Plato and Aristotle, Spinoza and Hegel. Herbert Spencer, however, not only betrays unconsciousness of this distinction, but employs it in far grosser and self-destructive applications. On page 25, (“First Principles,”) he says: “When on the sea shore we note how the hulls of distant vessels are hidden below the horizon, and how of still remoter vessels only the uppermost sails are visible, we realize with tolerable clearness the slight curvature of that portion of the sea’s surface which lies before us. But when we seek in imagination to follow out this curved surface as it actually exists, slowly bending round until all its meridians meet in a point eight thousand miles below our feet, we find ourselves utterly baffled. We cannot conceive in its real form and magnitude even that small segment of our globe which extends a hundred miles on every side of us, much less the globe as a whole. The piece of rock on which we stand can be mentally represented with something like completeness; we find ourselves able to think of its top, its sides, and its under surface at the same time, or so nearly at the same time that they seem all present in consciousness together; and so we can form what we call a conception of the rock, but to do the like with the earth we find impossible.” “We form of the earth not a conception properly so-called, but only a symbolic conception.” Conception here is held to be adequate when it is formed of an object of a given size; when the object is above that size the conception thereof becomes symbolical. Here we do not have the exact limit stated, though we have an example given (a rock) which is conceivable, and another (the earth) which is not. “We must predicate nothing of objects too great or too multitudinous to be mentally represented, or we must make our predications by means of extremely inadequate representations of such objects, mere symbols of them.” (27 page.)