External senses, for an external world. Internal senses, for Ideas, for the Mental, and Spiritual. If, then, we must have external eyes for external objects, should we not have spiritual eyes for spiritual subjects? . . . So we say of the Spirit and the Spirit World. Show us a spirit, let us see one! Well, now, let me ask,—Have you a mind? Let me see your mind. How will you convince me, that you have any mind, unless you show it to me? O, yes, you will exclaim, you will show your mind to one who has mental eyes to see it. MIND can be seen only by mind. True. And so we say of spirit. Spirits can be seen only by spiritual eyes, as external objects can be discerned only by external sight.