origin of intellectual life, and of the moral life; and show whether they are essentially different, or one and the same.

Then, how does human volition occasion the motion of parts of the human body, or of a separate body living or dead? How does mind operate upon nerves and muscles? How do nerves and muscles operate upon mind? Or, how is it that at the moment of volition I stretch out my arm, or rise from my seat; while no volition of mine will cause another man to stretch out his arm, or rise from his seat, unless his will concur with mine. Still farther, how is it that I cannot cause a heavy weight to move at my volition, without recurring to some mechanical process? I will the motion of a stone, it moves not: I will the motion of my arms, or my legs, or my eyes, they instantly obey. Why has my mind this power over the matter of my body, and not over other matter? I may be told, because there is an intimate connection between the substance which thinks, and the material substance in which it dwells. Be it so. 'Then what is that connection? Since it is certain that an immaterial substance cannot have with body the least point of contact; that thought cannot by communication become body, nor body become thought. Hence, then, an adequate cause of all the varieties of phenomema to which I have here adverted is as inscrutable, as deeply hidden among the mysteries, as the most recondite subject connected with religion.

Allow me next to proceed to a branch of knowledge in which opinions and theories are not daily fluctuating,

as are those in chemistry; I mean the mixed mathematical science of MECHANICS. This science is conversant about force, matter, time, motion, space. Each of these has been the cause of the most elaborate disquisitions, and of the most violent disputes. Let it be asked, what is force? If the answerer be candid, his reply will be, “I cannot tell, so as to satisfy every "inquirer, or so as to enter into the essence of the "thing." Again, what is matter? "I cannot tell." What is time? "I cannot tell." What is motion? "I cannot tell." What is space? "I cannot tell." Here, then, is a science, the professed object of which is to determine the mutual relations, dependencies, and changes of quantities, with the real nature of all of which we are unacquainted; and in which the professed object is, notwithstanding, effected. We have certain knowledge respecting subjects of which in themselves we have no knowledge: demonstrated, irrefragable propositions, respecting the relations of things, which in themselves elude the most acute investigations. The reason of this I shall attempt to assign by and bye. But before I proceed farther, I must request that you will acquit me of any intention to depreciate the sciences: on the contrary, they furnish me with daily delight; I know their value, have laboured long and actively in diffusing a knowledge of them, and am in some measure, I hope, able to appreciate their utility. I am also happy to affirm that in the physical sciences, and especially that to which our attention is now directed, very much has been accomplished. Yet I may challenge the wisest philoso

pher to demonstrate, from unexceptionable principles, and by just argument, what will be the effect of one particle of matter in motion meeting with another at rest, on the supposition that these two particles constituted all the matter in the universe. The fact of the communication of motion from one body to another is as inexplicable as the communication of divine influences. How, then, can the former be admitted with any face, while the latter is denied solely on the ground of its incomprehensibility? We know nothing of force any more than we do of grace, except by their effects. There are questions, doubts, perplexities, disputes, diversities of opinions, about the one as well as about the other. Ought we not, therefore, by a parity of reason, to conclude, that there may be several true and highly useful propositions about the latter as well as about the former? Nay, I will venture to go farther, and affirm, that the preponderance of argument is in favour of the propositions of the theologian. For while force, time, motion, &c. are avowedly constituent parts of a demonstrable science, and ought, therefore, to be presented in a full blaze of light, the obscure parts proposed for our assent in the Scriptures are avowedly mysterious. They are not exhibited to be perfectly understood, but to be believed. They cannot be explained, without ceasing to be what they are: for the explanation of a mystery is, as Dr. Young long ago remarked, its destruction. They cannot be rendered obvious without being made mean: for a clear idea is only another name for a little idea. Obscurities, however, are felt as incumbrances to any system of philoso

phy while mysteries are ornaments of the Christian system, and tests of the humility and faith of its votaries. So that, if the rejectors of incomprehensibilities acted consistently with their own principles, they should rather throw aside all philosophical theories in which obscurities are found, and exist as defects, than the system of Revealed Religion, in which they enter as essential parts of " that mystery of godliness" in which the Apostles gloried. (d)

But perhaps I may be told that although things which are incomprehensible occur in our physical and mixed inquiries, they have no place in "pure mathe"matics, where all is not only demonstrable, but "intelligible." This, again, is an assertion which I cannot admit; and for the denial of which I shall beg leave to produce my reasons, as this will, I apprehend,

(d) It has been asserted by a writer in the Monthly Review, in reply to all this, that to talk of "mysteries in revealed religion" is to frame a contradiction in terms. But this writer affects precision in language, without a corresponding precision in his ideas. It seems never to have entered into his mind, that a fact, either past, present, or to come, might be made known to us by express Revelation, which should nevertheless remain mysterious; the limits of our faculties, or perhaps the imperfection of language, rendering it inexpedient, or impossible, that it should be explained. Revelation may furnish us with clear evidence of the present existence of a truth, or the future occurrence of an event, though the thing itself may still remain incomprehensible to us. We have a striking example of this kind in Paul's First Epistle to the Corinthians, ch. xv. where he says, "Behold, I show you a mystery: we shall not all sleep; but we shall be changed, in a moment, in the twinkling of an eye, at the "last trump for the trumpet shall sound, and the dead shall be raised "incorruptible, and we shall be changed." Here he revealed a mystery: he revealed it, because it was till then unknown; it is notwithstanding a mystery, for there is not a syllable that explains to us how it will be effected.

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make still more in favour of my general argument. Now, here it is known geometricians can demonstrate that there are curves which approach continually to some fixed right-line, without the possibility of ever meeting it. Such, for example, are hyperbolas, which continually approach towards their asymptotes, but cannot possibly meet them, unless an assignable finite space can become equal to nothing. Such, again, are conchoids, which continually approach to their directrices, yet can never meet them, unless a certain point can be both beyond and in contact with a given line at the same moment. Mathematicians can also demonstrate that a space infinite in one sense may, by its rotation, generate a solid of finite capacity; as is the case with the solid formed by the rotation of a logarithmic curve of infinite length upon its axis, or that formed by the rotation of an Apollonian hyperbola upon its asymptote. They can also show in numerous instances that a variable space shall be continually augmenting, and yet never become equal to a certain finite quantity: and they frequently make transformations with great facility and neatness, by means of expressions to which no definite ideas can be attached. Can we, for example, obtain any clear comprehension, or indeed any notion at all, of the value of a power whose exponent is an acknowledged imaginary quantity, as x √ 1? Can we, in like tinct idea of a series constituted of an infinite number of terms? In each case the answer, I am convinced, must be in the negative. Yet the science, in which these and numerous other incomprehensibles occur, is

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