Ignorance hides from us facts, and we decide partially rather than confess our deficiency. Ill-directed education gives us pre-possessions, which are obstacles in the way of truth, and we continue to cherish what, having become a part of our nature, it pains us to discard. The senses will occasionally mislead us and although we are conscious that appearances are not to be wholly trusted, we reluctantly doubt our own infallibility. From early, and therefore unquestioned, associations, we have acquired certain habits, and from fashion certain sentiments, and we continue old customs, and fall into the current opinion unconsciously. Of these sources of prejudice, logic warns us to beware. Of so much importance did Bacon regard these hindrances to truth, that he considered the pursuit of new truth hopeless while they were cherished. In a mixed vein of poetry and philosophy, he divided prejudices into four classes, which he called Idols of the Tribe, the Den, the Market and the Theatre. Idols of the Tribe are prejudices men imbibe from early training, and love of hypothesis. They are so called because common to the whole race or tribe of mankind. Idols of the Den are those which relate to a man's particular character, Idols of the Market are those which are accommodated to common notions. Idols of the Theatre denote such as pertain to hypothetical systems of philosophy. Remembering the declarations of Euler and Gall, and the daily discoveries of science, we should stand, as it were, on the verge of the old world of experience, and look out on the new world of troth. A young thinker should make for himself a chart of proposed reforms, systems, and changes, agitated in his day--place In relative positions in the scale of importance such as he deems of value, if true--and then analyse his experience to see what is soundly opposed thereto. Such a practice would go far to rid men of idol-prejudices, which retard private improvement and public progress. CHAPTER XV. ILLUSTRATIVE EXERCISES 1. All men possessed of an uncontrolled discretionary power, leading to the aggrandisement and profit of their own body, have always abused it.'--Burke's Thoughts on the Present Discontents. The student will find the proof of this proposition exhibited in the example of Induction, quoted from Mr. Bailey, p. 63. 2. Prosperity could never be reached and maintained in this country, without some provision for the regular employment of the poor.--Mr. Beckett's Speech in the House of Commons, Feb. 3,1842. The demonstration, to universal conviction, of this proposition, would lead to an entire and beneficial change of the social condition of this country. 3. The pen is the tongue of the world.--Paine. Put this in the syllogistic form.