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terms notion, opinion, sentiment, conviction. How ought we to express ourselves in ordinary conversation with regard to these words?
LESSON 3. 16. Genus.--- Species. -- a. In comparing a large number of objects together, if I find that they all agree in some one particular, I class them together, and call the collection a Genus.-6. On further examination, if I observe, that though all these objects agree in some one particular, yet that they differ in others, I divide them, according to their resemblance to one another, into smaller parcels, and call these smaller parcels Species. On still further examination, each one of these species may become a genus, because the individuals comprehended under it will admit another division. And thus, we may divide and subdivide as long as there are common properties in which a few individuals or species agree.
17. When several genera are classed together, as agreeing in some properties which are common to all, they are considered as forming a superior genus; and of these superior genera, a still higher may be formed, and so on till we come to that which includes all subordinate genera, and is itself included by none. This is called by logicians Genus Summum. The genus summum thus includes several subordinate or inferior genera, and each of these may include others, and so on, till we come to the lowest collection of individuals.
18. That genus, which, in the scale of classification, is next above any species or genus, is called the Proximate Genus ; and that species which, in the descending scale, is next below, is called the Proximate Species. Thus, if the species is Zebra, the genus is Horse; the proximate genus is hoofed quadruped; the next higher is quadruped; the next is animal; and the highest, or genus summum, is being. If we make being the genus, animal will be the proximate species; if we make animal the genus, quadruped is the proximate species; and so in all the other cases.
19. Generic and Specific Difference. - That property or collection of properties, by which a species is distinguished from all other species under the same genus, is called the Specific Difference ; and, in like manner, the properties which distinguish the genus from all other genera under the same order or superior genus, is the Generic Difference. Thus, the species Zebra is distinguished from the other species of the horse tribe, by its having stripes on its back, and this circumstance constitutes its specific difference. The genus Horse is distinguished from all other hoofed animals, by its being whole hoofed ; this constitutes its generic difference.
20. Definition. — To define a thing is to mention those marks or characteristics by which it is infallibly distinguished from things that are similar to it. There are two kinds of definitions, the definition of words, and the definition of things. 21. Definition of Words.-a. A definition of a
-aa word is an explanation either in what sense the
word is used, or what idea or object we mean by it, and which may be expressed either by one or more of the properties, effects, or circumstances of that object, so as sufficiently to distinguish it from other objects.
b. Thus, were I to explain what is meant by the word air, I might say, it is that thin matter which we are continually inhaling or exhaling; or, it is that fluid body in which the birds fly a little above the earth. So, if I would explain what I meant by the word light, I might say, it is that medium whereby we see the colours and shapes of things; or, it is that which distinguishes the day from the night. These are called the definitions of the name.
c. Again, in defining a word, it is not necessary that we should explain the essence or nature of the thing; for any manner of description that will sufficiently acquaint another person what we mean by such a word, is a sufficient definition for the name.
A synonymous word, or a mere negative of the contrary, or sometimes a grammatical explication, is sufficient for this purpose ; thus, I might explain a sphere, by saying it is a globe; - a triangle, by saying it is a figure that has three angles;
- an asthma, a difficulty of breathing. 22. The Definition of Things.- a. The definition of a thing, is the explanation of its general nature, and those specific properties which distinguish it from every other thing.-6. We must, then, in the first place, discover the general nature in which a thing more immediately agrees with other things that most resemble it, and which is called the Proximate Genus. Next, we must discover the principal attribute, or quality, or property, which constitutes its essence, and in which it differs from those which most resemble it, - this
is called its Specific Difference. Join these together, and the definition will be completed. c. Thus, Object. Proximate Genus. Specific Difference. 1. A quadruped is
with four feet. 2. A square is a rectangle having all its sides equal. 3. Wine is
juice pressed from the grape. 4. A bird is
which flies in the air. 23. A definition should be precisely adequate to the term defined; the words employed should be clearer and better known than the term defined ; and, though no unnecessary terms should be émployed, yet, in definitions intended for those who are beginning any science, it is better to err on the side of diffuseness than to use terms which are not familiar. Thus, to define a square, a foursided figure having all its sides equal, and all its angles right angles, is much simpler than if I said, a square is an equilateral rectangle. Our sole object in a definition should be, to give a distinct, clear, and forcible representation or description of the thing signified.
QUESTIONS. — Explain the terms genus, species, superior genus, genus sumnum, inferior genera, proximate genus, proximate species. Adduce examples of each. Explain what is meant by specific difference ; — by generic difference. Give examples of each. What is meant by the term definition ? What is the definition of a word? Give examples. What is the definition of a thing? What rule is to be observed in defining things ? Give some examples. How should every definition be constructed ?
LESSON 4.— Exercises on Generic and Specific Difference.
24. a. Write down the generic difference between the following animals, according to Nos. 19, and 22.
Man, - horse, - bird, — fish.
6. Write the specific difference between the following according to Nos. 19. and 22.
1. Between a horse and a zebra.
LESSON 5. — Exercises on Definition. 25. Write down a definition of the following words, according to the directions given in No. 21. The definition must not consist of synonymous words, but be a clear and accurate explanation, so that the object can be at once distinguished from
1. Temperance. 5. Conscience. 9. Pride. 2. Industry. 6. Truth.
10. Avarice. 3. Perseverance. 7. Justice. 11. Lying. 4. Frugality. 8. Compassion. 12. Envy.
26. Write down a definition of the following things according to the directions given in No. 22.
1. A sheep. 5. A lemon. 9. A forest. 2. A horse. 6. A watch.
10. A cottage. 3. An eagle.
11. A park. 4. A shark. 8. Silver.
12. A garden.
7. An egg