Thought of a proposition is found in the content of that proposition. Hence, content of a proposition can be shared with thought of that proposition. In this connection, David Bell states that "if one sentence involves a concept that another sentence does not involve, the two sentences cannot express the same thought nor have the same content" (Bell, 1996, 588). Concerning this view, Frege affirms that thought is invariantly and logically related with propositions. As a result, we are able to determine the truth-value of propositions. A question is raised here, "Are thoughts same as ideas?" In order to resolve this problem Frege makes a distinction between 'thought' and 'idea'. On his view, ideas are subjective whereas thoughts are objective and eternal. The reasons are as follows:

1. Ideas cannot be seen, touched, smelled and tasted. It is the impression of an observer which stored in his/her mind. More precisely, ideas cannot be presented to our sense organs. For example, I saw a beautiful landscape. I have a visual impression on that landscape. I have it but I don't see it.


2. An idea, which someone has, belongs to the content of his or her consciousness. The contents might be in the form of sensations, feelings, moods, inclinations, wishes, etc. For example, suppose a person is very much fond of apple. Once he had gone to a fruit vendor to purchase apple. The fruit vendor arranges different varieties of fruits including apple in his rickshaw. The person who had gone to purchase apple may see different fruits arranged systematically in vendor's rickshaw, but his content of consciousness (alertness) is on apple. So the idea of apple exits for him. Thus, it is stated that without a bearer an idea cannot exit. In a similar fashion, an experience is not possible without an experiencer.


3. Things of the outer world are independent of its bearer. However, ideas need a bearer. Ideas are subjective. Since ideas are it subjective they differ from individual to individual. A particular object is recognized by some people. Their ideas on that particular object may differ from person to person because their approaches may differ to that object. For example, some people see an animal named 'Bucephalus' as a horse. Their ideas of that horse may differ, as the zoologist's idea of that animal 'Bucephalus' may differ from the idea of a poet, and the idea of a poet may differ from the idea of a horse rider and so on. Hence, each idea needs a bearer. Without a bearer an idea cannot exist.


4. Two individuals cannot have the same idea on a particular object because every idea needs only one bearer, and ideas are subjective. So, no two men have the same idea. For example, suppose I am having toothache and feel its pain. No other person can share my pain but someone may have sympathy for me. So here, my pain always belongs to me and his sympathy belongs to him. Hence, he does not have my pain and I do not have his sympathy. So, each idea has one and only one bearer. If it will be more than one, then ideas will be regarded as objective and universal, but it is not the case.