The content of a sentence exists independently of us but we can grasp them only by imposing propositional structure on them. According to Frege, contents are split into thoughts and truth-values. 'Truth-value' itself has no structure, whereas every thought has a specific content. Therefore, it is structured as Dummett says (Dummett, 1991, 305). Hence, it is widely accepted that the structure of a sentence serves as a model of the structure of a thought. In this connection, Russell asked Wittgenstein, if thoughts are well structured, can you elucidate the nature of thoughts and the elements that comprise them. It is cited as, "Russell wrote to the author of the Tractatus asking for elucidation about the nature of thoughts and the elements that comprises them. Wittgenstein replied, I don't know what the constituents of a thought are, but I know that it must have such constituents which correspond to the words of language" (Wittgenstein, 1974, 72). From this, it is presumed that each thought corresponds to the words of language.

Analyzing further, Frege argues that "if one sentence involves a concept that another sentence does not involve, the two sentences cannot express that same thought or have the same content" (Dummett, 1991, 295). In his words, to understand an expression is to grasp the sense of that expression.¹¹ It is so because "anyone who grasps the thought expressed by each of a given pair of synonymous sentences must immediately recognize one as true if he recognizes the other as true" (Dummett, 1991, 294).

Frege points out that 'truth' should not be confused with quality, because truth is not a quality. This could be explained with an example. Our everyday observation reveals that sun rises in the east and sets in the west, and it is true. Here, neither we perceive the object directly nor we gather all the properties of the rays of the sun. It is simply not possible to do so, yet we are claiming it is true. How is it possible to say so? Frege explains that we could not recognize the property of an object without at the same time realizing the thought of that object, i.e., this particular object has these sorts of properties and these are to be true for that object.

Frege has taken only indicative sentences for explaining the concept 'truth' because an indicative sentence contains something which is not found in other sentences, namely, 'assertion' and 'thought'. In this regard, he makes a distinction between interrogative sentence and indicative sentence. Interrogative sentences do not contain assertions whereas an indicative sentence states an assertion explaining thought.

Frege distinguishes the three following functions, namely, thinking, judging and asserting. As he puts it:

Apprehension of a thought----thinking
Recognition of the truth of a thought----judgment
Manifestation of this judgment----assertion¹²

¹¹	The term 'sense' and 'thought' are to be understood as same in the Fregean context. Hence, both can be used interchangeably.
¹²	Frege, G. (1977). Logical Investigations. In P.T. Geach, Oxford: Basil Blackwell Publication, p.7.