Nothing is more pleasant to the Fancy, than to enlarge it self by Degrees, in its Contemplation of the various Proportions [which [1]] its several Objects bear to each other, when it compares the Body of Man to the Bulk of the whole Earth, the Earth to the Circle it describes round the Sun, that Circle to the Sphere of the fixt Stars, the sphere of the fixt Stars to the Circuit of the whole Creation, the whole Creation it self to the infinite Space that is every where diffused about it; or when the Imagination works downward, and considers the Bulk of a human Body in respect of an Animal, a hundred times less than a Mite, the particular Limbs of such an Animal, the different Springs [which [2]] actuate the Limbs, the Spirits which set these Springs a going, and the proportionable Minuteness of these several Parts, before they have arrived at their full Growth and Perfection.  But if, after all this, we take the least Particle of these Animal Spirits, and consider its Capacity of being Wrought into a World, that shall contain within those narrow Dimensions a Heaven and Earth, Stars and Planets, and every different Species of living Creatures, in the same Analogy and Proportion they bear to each other in our own Universe; such a Speculation, by reason of its Nicety, appears ridiculous to those who have not turned their Thoughts that way, though at the same time it is founded on no less than the Evidence of a Demonstration.  Nay, we might yet carry it farther, and discover in the smallest Particle of this little World a new and inexhausted Fund of Matter, capable of being spun out into another Universe.

I have dwelt the longer on this Subject, because I think it may shew us the proper Limits, as well as the Defectiveness of our Imagination; how it is confined to a very small Quantity of Space, and immediately stopt in its Operations, when it endeavours to take in any thing that is very great, or very little.  Let a Man try to conceive the different Bulk of an Animal, which is twenty, from another which is a hundred times less than a Mite, or to compare, in his Thoughts, a length of a thousand Diameters of the Earth, with that of a Million, and he will quickly find that he has no different Measures in his Mind, adjusted to such extraordinary Degrees of Grandeur or Minuteness.  The Understanding, indeed, opens an infinite Space on every side of us, but the Imagination, after a few faint Efforts, is immediately at a stand, and finds her self swallowed up in the Immensity of the Void that surrounds it:  Our Reason can pursue a Particle of Matter through an infinite Variety of Divisions, but the Fancy soon loses sight of it, and feels in it self a kind of Chasm, that wants to be filled with Matter of a more sensible Bulk.  We can neither widen, nor contract the Faculty to the Dimensions of either Extreme.  The Object is too big for our Capacity, when we would comprehend the Circumference of a World, and dwindles into nothing, when we endeavour after the Idea of an Atome.