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tures a few steps farther. Revolving in his mind what he acknowledges has been done for man, the only rational inhabitant he knows on earth; and confidering that God has fent fome of his angels or meffengers from time to time to declare his will to us; and has moreover fent the Chrift more fully to reveal it; whatever others may think, he is satisfied thereby that however small we are in this vast universe, we are not beneath the notice of the Ruler of it. Loft in amaze at the greatness, and at the fame time the goodness of the Deity towards us, will he not be led thereby into a more full acknowledgment of him, and more determined refolution of obedience to his will? This feems but the rational refult from fuch a chain of thought.

Yet, if that thought be pursued, fince the inhabitants of the other planets of our fyftem, and of the many systems there may be among the numberlefs ftars in the vast expanfe, muft equally be objects of the Divine favour with ourselves; and fince the rational inhabitants of fome few or more among fo many myriads, may have been found difobedient; is a man to blame for thinking that if they ftand in need of restoration, they must be full as worthy of it as ourfelves; and may, for any thing that we know, have been already redeemed, or may yet be to be redeemed, when and in what way it fhall be feen fitting by the Almighty Ruler of us all?

LECTURE

THE

LECTURE XLV.

ON PHYSICAL ASTRONOMY. *

HE caufes of the celeftial motions have in all ages been the objects of philofophical curiofity. Men have generally conducted their researches on this fubject upon principles of analogy. Some refemblances have been noticed between the motions of the celestial bodies, and other motions nearer at hand, and more familiar to us; and the fame refemblances have been fuppofed to exift between their causes.

I fhall notice four of these different refemblances, or analogies.

1. The motions of the heavenly bodies have been thought to resemble the fpontaneous motions of intelligent beings. Ariftotle, Leibnitz, Tucker, Monboddo, and fome others, both in ancient and modern times, have taught, that the planets were conducted by fpiritual intelligent beings.

Though accounts of the celeftial phenomena may be given by means of this refemblance, that are chargeable with no false reasoning; yet as they afford no explanation, they anfwer no purpose in philofophy.

2. The celeftial motions have been thought to represent the motions of bodies carried about centers by means of folid connections.

This notion fuggefted to philofophers the opinion, that the planets were attached to folid orbs, which turn round the axis of revolution: this opinion

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* Profeffor Robifon's Outlines of Mechanical Philofophy, page 105.

opinion has been falfely attributed to Ariftotle. It is altogether contradictory to our ideas of the etherial matter that occupies celeftial space, and not cafily reconcilcable to the elliptic motion of the planets.

3. The celeftial motions have been thought to resemble the motions of bodies carried round by a circulating fluid. Many philofophers have fuppofed the planets to be carried round in fuch vortices. Dejcartes and Leibnitz were at great pains to eftablish this doctrine. More modern writers * have removed the difficulties, and obviated the objections made to this fyftem. It will therefore be neceffary to lay before you fome of the arguments urged in it's favour; in doing this, I fhall be under the neceflity of repeating fome obfervations that I have before made.

Thefe writers urge, that fo long as we keep within the limits of natural and experimental philofophy, we must account for the motions in nature, by referring them to corporeal caufes; and where this cannot be performed fatisfactorily, we must give them up, or wait with patience for fome better clue of investigation, or fome further light from experience. It is contrary to found philofophy to amufe ourselves with nanies and qualities, which contradi&t the known laws of mechanifm, and fuperfede the operation of the elements.

Nothing is intelligible in philofophy but the action of matter upon matter; the power of impulse is the only fenfible and experimental caufes of motion; and there is the ftrongest prefumption from analogy in favour of the univerfal material mechanifm of the operations of nature. All other principles of motion are founded on conjecture, and in

capable

* Jones's Phyfiological Difquifitions; Effay on the First Principles of Natural Philofophy; Dr. A. Wilton's Obfervations on the Moving Powers of the prefent System.

capable of proof. If you attempt to foar above this principle in theory, you are always obliged to defcend to it in practice. Natural philofophy has been principally advanced by the experiments which have been made on the elements; but these experiments prove, that matter interferes in producing all the changes and motions that are obferved in bodies diftant from each other.

Look into, and obferve the operations in nature: how does the fun act upon the fruits of the earth, but by the mediation of it's light? How do the clouds water the earth, but by the mediation of air? How does the chemift produce fuch wonderful changes in natural bodies, but by the mediation of fire? In a word, every experiment, every obfervation proves, that in all cafes where diftant bodies are found to affect each other, there is always fomething to mediate, whether we do or do not perceive it; and when this mediation can be no further traced, natural philofophy is at an end, and the fictions of imagination begin, which are of equal value, by whatever name they may be called, or with whatever parade of demonftration they may be introduced.

It is very fingular, they obferve, that inquirers after phyfical truth fhould obferve and acknowledge mechanifm in the greater part of nature, and yet not be led thereby to inquire, whether it be not univerfally extended; the more fo, as matter and motion must have the fame invariable properties. If vapour rifes mechanically, why may not a flone defcend by the fame law? If fluids circulate in organized bodies by continued impulfe, why may not a planet revolve in the organized fyftem of the univerfe by the fame caufe?

All true philofophers agree in confidering the univerfe as great machine, fo created, fitted, and difpofed power of GoD, as to perform all

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the

the operations which are carried on throughout the whole. There is a connection and communication between all the diftant parts thereof. No one part can be confidered as acting without being acted

upon.

It is highly unphilofophical to affert, that matter, confidered in general, or any part thereof, has effential jeparate qualities, by which one part acts upon another. It is the effential property of no one wheel in a machine to move it's fellow, though in confequence of it's being placed in the ftation it is fitted for, it acts upon it's fellow, because it is acted upon. If you interrupt the contac in a machine, you deftroy the motion in all those parts where the communication is destroyed.

It is just the fame with the whole fyftem of nature, you cannot take up any parcel of matter, and fay of it, this has effential properties which empower it to be a natural agent. A philofopher ought to confider it as a concrete, with a certain difpofition of parts liable to be acted upon by the fubtiler parts of the machine, which can by no means be restrained by art therefrom. It might be as juftly afferted, that it is the effential property of animal fubances to live, as that it is the effential property of the loadstone to attract.

The promoters of the opinion now under confideration, urge further, that every known operation in nature is mechanical; and that in all experiments, where the explanation is clear and certain, the effects are produced by matter acting upon matter; and we are able to trace this mechanifm in fuch a variety of inflances, that unlefs the world, is governed by oppofite and contradictory principles, it muft obtain throughout

the whole.

Thus the body of man, which is the highest piece of machinery in nature, is made to fee, to

bear,

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