Deduction has two parts. [—] Explication is followed by Demonstration, or Deductive Argumentation. [—] It invariably requires something of the nature of a diagram; that is, an “Icon,” or Sign that represents its Object in resembling it. It usually, too, needs “Indices,” or Signs that represent their Objects by being actually connected with them. But it is mainly composed of “Symbols,” or Signs that represent their Objects essentially because they will be so interpreted. Demonstration should be Corollarial when it can. An accurate definition of Corollarial Demonstration would require a long explanation; but it will suffice to say that it limits itself to considerations already introduced or else involved in the Explication of its conclusion; while Theorematic Demonstration resorts to a more complicated process of thought.