A fundamental objection to my position on assertion (that assertion is a part of the semantics of a declarative sentence) is that assertion must be personal. That is, the subject of verbs like 'assert', 'state', 'say' and suchlike must be a person. Thus no sentence - which is an impersonal, inanimate linguistic item - can assert anything. Thus assertion cannot be part of the semantics of a sentence.
I shall argue against this in two ways.
1. Even if we concede that the subject of an assertion must be personal, it does not follow that we cannot analyse a sentence in such a way that a sign for assertion is made visible. I claim that we can analyse the sentence 'Tom runs' as
It is true / that Tom runs
which means the same, but which contains the sign 'it is true'. The other part is the that-clause 'that Tom runs', which signifies the content of the sentence. This is the same content referred to in sentences such as 'Alice believes that Tom runs', 'Carol hopes that Tom runs', 'Bob doubts that Tom runs' and so on. But no one who utters these sentences asserts that content. If I utter 'Alice believes that Tom runs', I have asserted that Alice believes something. But I have not asserted the thing that she believes: I have not asserted that Tom runs, only that Alice believes this. But when I utter 'It is true that Tom runs', I have asserted that Tom runs. Which suggests that 'it is true' is a sign indicating that I am asserting the content itself, rather than saying something about it (such that it is a belief, or a hope, of someone). The sign 'it is true' is a symbol which, suitably connected with a symbol for the content, signifies assertion.
2. In any case, we need the idea of impersonal assertion for statements whose author is unknown. For example "The next sentence in Genesis says the earth was without form and void, and darkness over it.
In summary. We can analyse a declarative sentence into another sentence which means the same, but which has two main parts: a sign for the content of the sentence and another sign which is used to indicate or signify that the speaker is personally asserting the content, rather than saying something about the content. It is not unreasonable to call this an assertion sign. And sometimes - when the author of the original sentence is unknown - it is equally reasonable to say that the sentence impersonally asserts its content.