The Point of Assertion
It can seem initially attractive that truth licenses assertion. If the purpose of assertion is to convey accurate information then simple logic dictates that it is natural to think that any true proposition is assertible. Yet this underestimates the extent to which an assertion is a normative social practice rather than a semantic one. Assertions are not simply stating truths but presenting them as something that can be digested by specific audiences from a particular epistemic position.
This suggests an initial constraint on an assertion. Where a speaker who asserts a true proposition while lacking any sound epistemic basis will misrepresent their position as someone who understands the assertion. Even if the audience acquires a true belief, there has been error in the act of the assertion itself. This raises doubt on the notion that truth alone can justify assertions.
Epistemic Responsibility
As Weiner observes, asserting a proposition usually represents the speaker as being entitled to it in some epistemic way (Weiner, 2007). This explains why lucky guesses, even when true, are not set for assertion — the problem is not the truth of what is said, but rather the disparity between the assertion and the speaker's epistemic position. Assertion therefore functions as an epistemic guarantee to some audience and where that guarantee is unwarranted, the assertion is non-functional even if it is true.
However, epistemic entitlement alone cannot fully account for when truths ought not to be asserted. There are some instances where the speaker knows that a proposition is true, yet asserting it still seems inappropriate. This implies that epistemic responsibility is mono-dimensional regarding the norms which govern assertion. To further explain these specific instances we must examine how assertions operate inside different contexts.
Misleading Truths
Grice provides an account of conversational implicature which offers reasoning for how a true assertion can nonetheless be objectionable. As per Grice, "cooperative conversation" is governed by maxims such as Quantity and Relation, which lead hearers to infer more than what is strictly said (Grice, 1989). As audiences reasonably assume that speakers are being somewhat informative and relevant, speakers can create misleading implications without asserting anything explicitly false. As Blome-Tillmann writes, this makes it possible to deceive while speaking the truth (Blome-Tillmann, 2013).
A speaker may assert a proposition that is true but incomplete, assuming that the audience will draw a false conclusion. What makes such a case problematic is not simply that a conversational norm has been violated but that the speaker knowingly relies on the audience's cooperation to infer error. These instances show that there are truths that one should not assert because of the pragmatic consequences of asserting them. Even when a speaker knows the proposition and asserts it with full sincerity, the effect of the assertion is still to mislead. This shows that assertability depends not only on truth and knowledge but additionally on the communicative role that an assertion carries in context.
Conditionality of Assertions
Assertions are not simply a conduit for transmitting true propositions but are interventions in an epistemic context. As such, speakers carry responsibility not only for what they say, but for how their words are taken by others. This suggests that a speaker should not assert a proposition, even if it is true and known, when they can reasonably foresee that asserting it will lead their audience to form a false belief.
This explains why lucky guesses are not permissible for assertions, and why misleading truths are problematic, and why certain context-reliant truths should not be asserted despite being known.
Morals of Truthful Assertion
The moral significance of such a failure is emphasised by Saul and Stokke. Saul argues that restricting moral evaluation to lying overlooks a wide range of deceptive speech acts that operate through true assertions (Saul, 2012). If a speaker knowingly induces a false belief by asserting a truth, then the fact that no false statement was made does not absolve them of responsibility. From the audience's perspective, the epistemic harm is the same.
Stokke similarly distinguishes lying from misleading whilst still maintaining that misleading can be morally objectionable even when it involves no falsehoods (Stokke, 2013). This supports the aforementioned conditionality by showing that speakers are accountable for the predictable effects of their assertions, not simply for their semantic content. The "wrongness" of such assertions lies not in their falsity, nor necessarily in the speaker's lack of knowledge, but rather in the mismanagement of shared epistemic norms.
Conclusion
The question of whether there are truths that one should not assert seems simple once assertion is understood as a norm-governed social practice. Whilst truth is a necessary condition for proper assertion, it is not sufficient. Assertions represent speakers as epistemically entitled and shape the epistemic environment of their audience. When asserting a truth would misrepresent one's epistemic position or foreseeably mislead an audience, that truth ought not to be asserted. The main notion then is that assertability depends not only on what is true, but on how truth is responsibly communicated. Therefore there are indeed some truths that one should not assert.
Bibliography
Blome-Tillmann, M. (2013). "Conversational Implicatures (and How to Spot Them)." Philosophy Compass 8(2): 170–185.
Grice, H. P. (1989). Studies in the Way of Words. Cambridge, MA: Harvard University Press.
Saul, J. (2012). "Just Go Ahead and Lie." Analysis 72(1): 3–10.
Stokke, A. (2013). "Lying, Deceiving, and Misleading." Philosophy Compass 8(4): 348–359.
Weiner, M. (2007). "Norms of Assertion." Philosophy Compass 2(2): 187–195.