But before we proceed further, it behoves us to answer the objections contained in the following passage, or withdraw ourselves in time from the bitter contempt in which it would involve us. Acting under such a necessity, we need not apologise for the length of the quotation.
1. “If,” says Mr. Lawrence, “the properties of living matter are to be explained in this way, why should not we adopt the same plan with physical properties, and account for gravitation, or chemical affinity, by the supposition of appropriate subtile fluids? Why does the irritability of a muscle need such an explanation, if explanation it can be called, more than the elective attraction of a salt?”
2. “To make the matter more intelligible, this vital principle is compared to magnetism, to electricity, and to galvanism; or it is roundly stated to be oxygen. 'Tis like a camel, or like a whale, or like what you please.”
3. “You have only to grant that the phenomena of the sciences just alluded to depend on extremely fine and invisible fluids, superadded to the matters in which they are exhibited, and to allow further that Life, and magnetic, galvanic, and electric phenomena correspond perfectly; the existence of a subtile matter of Life will then be a very probable inference.”
4. “On this illustration you will naturally remark, that the existence of the magnetic, electric, and galvanic fluids, which is offered as a proof of the existence of a vital fluid, is as much a matter of doubt as that of the vital fluid itself.”
5. “It is singular, also, that the vital principle should be like both magnetism and electricity, when these two are not like each other.”
6. “It would have been interesting to have had this illustration prosecuted a little further. We should have been pleased to learn whether the human body is more like a loadstone, a voltaic pile, or an electrical machine; whether the organs are to be regarded as Leyden jars, magnetic needles, or batteries.”
7. “The truth is, there is no resemblance, no analogy, between Electricity and Life; the two orders of phenomena are completely distinct; they are incommensurable. Electricity illustrates life no more than life illustrates electricity.”[13]
To avoid unnecessary description, I shall refer to the passages by the numbers affixed to them, for that purpose, in the margin.
In reply to No. 1, I ask whether, in the nature of the mind, illustration and explanation must not of necessity proceed from the lower to the higher? or whether a boy is to be taught his addition, subtraction, multiplication, and division, by the highest branches of algebraic analysis? Is there any better way of systematic teaching, than that of illustrating each new step, or having each new step illustrated to him by its identity in kind with the step the next below it? though it be the only mode in which this objection can be answered, yet it seems affronting to remind the objector, of rules so simple as that the complex must even be illustrated by the more simple, or the less scrutible by that which is more subject to our examination.