In Arthur Schopenhauer’s The World as Will and Representation, we find a discussion of how he views ‘the subject’ as one single entity:
Therefore the world as representation, in which aspect alone we are here considering it, has two essential, necessary, and inseparable halves. The one half is the object, whose forms are space and time, and through these plurality. But the other half, the subject, does not lie in space and time, for it is whole and undivided in every representing being.
What Schopenhauer might have on mind isn’t the grammatical subject but the sentient being.
The grammatical subject
Subject as opposed to the predicate, is a grammatical unit consisting of a noun or pronoun which represents the entity performing the action. Example:
The noun ‘Jesus’ is the subject and the conjugated verb ‘wept’ is the predicate.
The definition of ‘subject’ stated above is a temporary definition, for as we are going to show, the English sentence permits other grammatical units -besides nouns or pronouns- to act as subjects.
Nouns and pronouns as subjects
When subjects are nouns or pronouns, they are quite visible and they may be easy to spot. In the following sentence we can unequivocally see that ‘Dick and I’ are the subjects of the sentence.
Dick and I went to the game on Sunday.
‘Dick’ of course is a noun or a nickname (if you will), and I, a personal pronoun.
Now, let’s try to spot the sentence in the following example:
Justice is blind.
‘Justice’ is a noun and precedes the verb ‘is.’ However, the noun ‘justice’ is an abstract noun and being an abstraction it is invisible. Yet, by its position and its function we may see that it is the subject of the sentence.
a) The self and the ego are Freudian inventions.
b) Daffodils bloom in the spring.
c) Dawn broke.
By way of summary of the above discussion, let’s agree: while the subjects in the example (a) are the ‘self’ and the ‘ego,’ the subject in example (b) are the ‘daffodils,’ and ‘Dawn’ in example (c). We can now generalize and say that nouns -both concrete and abstract- are often the subjects of sentences.
Imperatives as subjects
Don’t do that!
Note that ‘Don’t’ precedes the verb ‘do’ and it is acting as the subject of the sentence.
Let’s not argue about that!
Again, ‘Let’s not’ precedes the verb ‘argue’ and acts as the subject of the sentence.
Verbals as subjects
a) To own riches is the poor man’s dream
b) To see it through is difficult if not impossible
c) Picking a fight with a child is cowardly
In example (a) ‘To own riches’ is an infinitive verbal acting as the subject, and is ‘To see it through,’ in example (b). In example (c) ‘Picking a fight’ is a present participle acting as the subject of the sentence.
The peculiar feature of these verbals being used as subjects, corroborates Schopenhauer’s intuition that some subjects do not lie in space and time, but are mental constructs.
The subjects of the English sentence fall into five groups:
Verbals (infinitives and participles)
Subject as opposed to the predicate, is a grammatical unit consisting of a noun (concrete or abstract), a personal pronoun, imperatives, and verbals which do not lie in space and time.