Infinitives and participles which are the infinite parts of the verb cannot be predicates. "I looking up the street" is not a sentence, for it is not a complete action expressed. When we hear such an expression as "A dog running along the street," we wait for something more to be added, something more affirmed about the dog, whether he bit or barked or fell dead or was run over.
Thus in every sentence there must be a finite verb to limit the subject.
When the verb is transitive, that is, when the action cannot happen without affecting something, the thing affected is called the object.
Thus in "Cain killed Abel" the action of the killing affected Abel. In "The cat has caught a mouse," mouse is the object of the catching.
ARRANGEMENT OF WORDS IN A SENTENCE
Of course in simple sentences the natural order of arrangement is subject—verb—object. In many cases no other form is possible. Thus in the sentence "The cat has caught a mouse," we cannot reverse it and say "The mouse has caught a cat" without destroying the meaning, and in any other form of arrangement, such as "A mouse, the cat has caught," we feel that while it is intelligible, it is a poor way of expressing the fact and one which jars upon us more or less.
In longer sentences, however, when there are more words than what are barely necessary for subject, verb and object, we have greater freedom of arrangement and can so place the words as to give the best effect. The proper placing of words depends upon perspicuity and precision. These two combined give style to the structure.
Most people are familiar with Gray's line in the immortal Elegy—"The ploughman homeward plods his weary way." This line can be paraphrased to read 18 different ways. Here are a few variations:
Homeward the ploughman plods his weary way.
The ploughman plods his weary way homeward.
Plods homeward the ploughman his weary way.
His weary way the ploughman homeward plods.
Homeward his weary way plods the ploughman.
Plods the ploughman his weary way homeward.
His weary way the ploughman plods homeward.
His weary way homeward the ploughman plods.
The ploughman plods homeward his weary way.
The ploughman his weary way plods homeward.
and so on. It is doubtful if any of the other forms are superior to the one used by the poet. Of course his arrangement was made to comply with the rhythm and rhyme of the verse. Most of the variations depend upon the emphasis we wish to place upon the different words.