When you converse with another person about some particular thing, that thing is the subject of your conversation. What a lecturer talks about is the subject of his lecture. You choose subjects for your compositions. When any one makes a single assertion, he has a thought; and the thing that he makes the assertion about is the subject of his thought. In answering the first question of the preceding exercise, you told in regard to each sentence what the speaker's subject of thought was; - for example, the speaker of Sentence 1 made his assertion about all birds, and they were his subject of thought; the speaker of Sentences 3 and 4 was thinking of some particular birds only, and these birds were the subject of his thought; the speaker of expression 6 had Columbus for the subject of his thought. You will now understand the following definition:

That about which a particular assertion is made is the subject of thought.

Anything about which an assertion can be made is a subject of thought, whether an assertion is made about it or not.

The sentence, Mary admired the beauty of the flower, mentions three subjects of thought, - Mary, the beauty of the flower, and the flower itself. The assertion is made about Mary, therefore she is the subject of thought. But an assertion can be made about each of the other two subjects of thought. Show that it can.