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April 10, 2026
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"By far the most valuable things, which we know or can imagine, are certain states of consciousness, which may roughly be described as the pleasures of human intercourse and the enjoyment of beautiful objects. No one, probably, who has asked himself the question, has ever doubted that personal affection and the appreciation of what is beautiful in Art or Nature, are good in themselves; nor, if we consider strictly what things are worth having purely for their own sakes, does it appear probable that any one will think that anything else has nearly so much value as the things which are included under these two heads."
"The study of Ethics would, no doubt, be far more simple, and its results far more "systematic," if, for instance, pain were an evil of exactly the same magnitude as pleasure is a good; but we have no reason whatever to assume that the Universe is such that ethical truths must display this kind of symmetry ... ."
"I can prove now, for instance, that two human hands exist. How? By holding up my two hands, and saying, as I make a certain gesture with the right hand, "Here is one hand," and adding, as I make a certain gesture with the left, "and here is another." And if, by doing this, I have proved ipso facto the existence of external things, you will all see that I can also do it now in numbers of other ways: there is no need to multiply examples."
"It is raining but I do not believe that it is."
"Among the foundations of the Higher Mathematics is also the 'Idea of a Limit'. The Idea of a Limit cannot be superseded by any other definitions or Hypotheses."
"The Idea of Cause is expressed for purposes of science by these three Axioms:—'Every Event must have a Cause':—'Causes are measured by their Effects':—'Reaction is equal and opposite to Action'."
"'Intuitive' is opposed to 'discursive' reason. In intuition, we obtain our conclusions by dwelling upon 'one' aspect of the fundamental Idea; in discursive reasoning, we combine several aspects of the Idea"
"'Form' or 'figure' is space limited by boundaries. Space has necessarily 'three' dimensions, length, breadth, depth; and no ethers which cannot be resolved into these."
"The Perception of Time involves a constant and latent kind of memory, which may be termed a 'Sense of Succession'. The Perception of Number also involves this Sense of Succession, although in small numbers we appear to apprehend the units simultaneously and not successively."
"Mechanical Science depends on the Conception of Force; and is divided into 'Statics', the doctrine of Force preventing motion, and 'Dynamics', the doctrine of Force producing motion."
"In order to acquire any exact and solid knowledge, the student must possess with perfect precision the ideas appropriate to that part of knowledge: and this precision is tested by the student's 'perceiving' the axiomatic evidence of the 'axioms' belonging to each 'Fundamental Idea'."
"Truths once obtained by legitimate Induction are Facts: these Facts may be again connected, so as to produce higher truths: and thus we advance to 'Successive Generalizations'."
"Truths obtained by Induction are made compact and permanent by being expressed in 'Technical Terms'."
"The Sensations are the 'Objective', the Ideas the 'Subjective' part of every act of perception or knowledge."
"'When two equal weights are supported on the middle point between them, the pressure on the fulcrum is equal to the sum of the weights.'"
"Man, servant and interpreter of Nature, does and understands only as much as he has observed of the order of Nature, either in reality or in mind; he neither knows nor can do more."
"The antithesis of 'Sense' & 'Ideas' is the foundation of the Philosophy of Science. No knowledge can exist without the union, no philosophy without the separation, of these two elements."
"In Deductive Reasoning, we cannot have any truth in the conclusion which is not virtually contained in the premises."
"By speaking of space as an Idea, I intend to imply the apprehension of objects as existing in space, and of the relations of position prevailing among them, is not a consequence of experience but a result of a peculiar constitution and activity of the mind which is independent of all experience in its origin, though constantly combined with experience in its exercise."
"A scientific writer of modern times appears to wonder that men did not at once divine the weight of the air from which the phenomena formerly ascribed to the 'fuga vacui' really result. “Loaded, compressed by the atmosphere,” he says, “they did not recognize its action. In vain all Nature testified that air was elastic and heavy; they shut their eyes to her testimony. The water rose in pumps and flowed in siphons at that time as it does at this day. They could not separate the boards of a pair of bellows of which the holes were stopped; and they could not bring together the same boards without difficulty if they were at first separated. Infants sucked the milk of their mothers; air entered rapidly into the lungs of animals at every inspiration; cupping-glasses 'produced tumours on the skin; and in spite of all these striking proofs of the weight and elasticity of the air, the ancient philosophers maintained resolutely that air was light, and explained all these phenomena by the horror which they said Nature had for a vacuum.” It is curious that it should not have occurred to the author while writing this, that if these facts, so numerous and various, can all be accounted for by one principle, there is a strong presumption that the principle is not altogether baseless. And in reality is it not true that Nature does abhor a vacuum, and do all she can to avoid it? No doubt this power is not unlimited; and we can trace it to a mechanical cause, the pressure of the circumambient air. But the tendency, arising from this pressure, which the bodies surrounding a space void of air have to rush into it, may be expressed, in no extravagant or unintelligible manner, by saying that Nature has a repugnance to a vacuum."
"We unfold out of the Idea of Space the propositions of geometry, which are plainly truths of the most rigorous necessity and universality. But if the idea of space were merely collected from observation of the external world, it could never enable or entitle us to assert such propositions: it could never authorize us to say that not merely some lines, but all lines, not only have, but must have, those properties which geometry teaches. Geometry in every proposition speaks a language which experience never dares to utter; and indeed of which she but half comprehends the meaning."
"Every failure is a step to success. Every detection of what is false directs us towards what is true: every trial exhausts some tempting form of error. Not only so; but scarcely any attempt is entirely a failure; scarcely any theory, the result of steady thought, is altogether false; no tempting form of Error is without some latent charm derived from Truth."
"According to the technical language of old writers, a thing and its qualities are described as subject and attributes; and thus a man’s faculties and acts are attributes of which he is the subject. The mind is the subject in which ideas inhere. Moreover, the man’s faculties and acts are employed upon external objects; and from objects all his sensations arise. Hence the part of a man’s knowledge which belongs to his own mind, is subjective: that which flows in upon him from the world external to him, is objective."
"Our assent to the hypothesis implies that it is held to be true of all particular instances. That these cases belong to past or to future times, that they have or have not already occurred, makes no difference in the applicability of the rule to them. Because the rule prevails, it includes all cases."
"We cannot observe external things without some degree of Thought; nor can we reflect upon our Thoughts, without being influenced in the course of our reflection by the Things which we have observed."
"The system becomes more coherent as it is further extended. The elements which we require for explaining a new class of facts are already contained in our system. Different members of the theory run together, and we have thus a constant convergence to unity. In false theories, the contrary is the case."
"The Science of Hydrostatics depends upon the Fundamental Principle that 'fluids press equally in all directions'. This Principle necessarily results from the conception of a Fluid, as a body of which the parts are perfectly moveable in all directions. For since the Fluid is a body, it can transmit pressure; and the transmitted pressure is equal to the original pressure, in virtue of the Axiom that Reaction is equal to Action. That the Fundamental Principle is not derived from experience, is plain both from its evidence and from its history."
"And so no force however great can stretch a cord however fine into an horizontal line which is accurately straight."
"We necessarily perceive bodies as 'without' us: the Idea of 'Externality' is one of the conditions of perception."
"Secondary Qualities are not 'extended' but 'intensive'; their effects are not augmented by addition of parts, but by increased operation of the medium. Hence they are not measured directly, but by 'scales'; not by 'units', but by 'degrees'."
"We perceive by 'means' of a medium and 'by means' of impressions on the nerves: but we do not (by our senses,) perceive either the medium or the impressions on the nerves."
"Many glaring errors of the Greeks will have to be noticed ... few of them can be referred to the cause assigned by Dr. Whewell."
"When alterations in technical terms become necessary, it is desirable that the new term should contain in its form some memorial of the old one."
"The fundamental terms of a system of Nomenclature may "be conveniently borrowed from casual or arbitrary circumstances."
"In forming a Terminology, words may be invented when necessary, but they cannot be conveniently borrowed from casual or arbitrary circumstances."
"[P]hilological analogies are to be preserved if possible, but modified according to scientific convenience."
"Terms must be constructed and appropriated so as to be fitted to enunciate simply and clearly true general propositions."
"New terms and changes of terms, which are not needed in order to express truth, are to be avoided."
"It is better to form new words as technical terms, than to employ old ones in which the last three Aphorisms cannot be complied with."
"Terms which imply theoretical views are admissible, as far as the theory is proved."
"If terms are systematically good, they are not to be rejected because they are etymologically inaccurate."
"'The Law of Continuity' is this:—that a quantity cannot pass from one amount to another by any change of conditions, without passing through all intermediate magnitudes according to the intermediate conditions. It may often be employed to disprove distinctions which have no real foundation. 'The Method of Gradation' consists in taking a number of stages of a property in question, intermediate between two extreme cases which appear to be different. It is employed to determine whether the extreme cases are really distinct or not. 'The Method of Gradation', applied to decide the question, whether the existing phenomena arise from existing causes, leads to this result:—That the phenomena do appear to arise from existing causes, but that the action of existing causes have transgressed their recorded Limits of Intensity. 'The Method of Natural Classification' consists in classing cases, not according to any assumed definition, but according to the connexion of the facts themselves."
"In the 'Induction of Causes' the principal maxim is, that we must be careful to possess, and to apply, with perfect clearness, the Fundamental Idea on which the Induction depends. The Induction of Substance, of Force, of Polarity, go beyond mere laws of phenomena, and may be considered as the Induction cf Causes. The Cause of certain phenomena being inferred, we are led to inquire into the Cause of this Cause, which inquiry must be conducted in the same manner as the previous one; and thus we have the Induction of Ulterior Causes."
"The Construction of the Conception very often includes, in a great measure, the Determination of the Magnitudes. The true construction of the conception is frequently suggested by some hypothesis; and in these cases, the hypothesis may be useful, though containing superfluous parts."
"In the Ancient Period of Science, Technical Terms were formed in three different ways:—by appropriating common words and fixing their meaning;—by constructing terms containing a description;—by constructing terms containing reference to a theory."
"The Methods of Observation of Quantity in general, are 'Numeration', which is precise by the nature of Number; the 'Measurement of Space' and 'of Time', which are easily made precise; the 'Conversion of Space and Time', by which each aids the measurement of the other. The Idea of Space becomes more clear by studying 'Geometry'; the Idea of Force, by studying 'Mechanics'; the Ideas of Likeness, of Kind, of subordination of Classes, by studying 'Natural History'."
"'Natural History' ought to form a part of intellectual education, in order to correct certain prejudices which arise from cultivating the intellect by means of mathematics alone and in order to lead the student to see that the division of things into kinds, and the attribution and use of names, are processes susceptible of great precision."
"In framing scientific terms, the appropriation of old words is preferable to the invention of new ones."
"The Process of Induction may be resolved into three steps ; the 'Selection of the Idea', the 'Construction of the Conception', and the 'Determination of the Magnitudes'. These three steps correspond to the determination of the 'Independent Variable', the 'formula', and the 'coefficients', in mathematical investigations; or to the 'Argument', the 'Law', and the 'Numerical Data', in a Table of an Inequality. The conceptions involved in scientific truths have attained the requisite degree of clearness by means of the Discussions respecting ideas which have taken place among discoverers and their followers. Such discussions are very far from being unprofitable"
"'Induction' is a term applied to describe the 'process' of a true Colligation of Facts by means of an exact and appropriate Conception. 'An Induction' is also employed to denote the 'proposition' which results from this process. An Induction is not the mere sum of the Facts which are colligated. The Facts are not only brought together, but seen in a new point of view. 'The Consilience of Inductions' takes place when an Induction, obtained from one class of facts, coincides with an Induction, obtained from another different class."