The first sonnet of Sidney's sequence "Astrophil and Stella" explores the failure of the poet's artifice in reflecting the truth and ends with an implied pledge of sincerity as the Muse tells the speaker, Astrophil, to "look in thy heart and write."
As this first sonnet implies, the relationship between truth and artifice is not necessarily antagonistic. On the contrary, Astrophil laments that he does not possess sufficient artistry to depict the truth in his verse. This is a problem which keeps resurfacing throughout the sequence. In Sonnet 11, for instance, he complains that his depiction of his own emotions seems too "boyish" and, by implication, insincere. However, on the other hand, he contrasts his own sincerity with those more conventional poets who write by the "dictionary's method" in Sonnet 15.
The overall impression conveyed by the sequence is that of a lover who is sincere and anxious to tell the truth but not entirely sure how to do so. The relationship between truth and sincerity is not straightforward: writing from the heart does not necessarily mean portraying the truth. Although he is told to look in his heart and write, Astrophil finds himself using all manner of artifice. The challenge is not to abandon this altogether, but to write with an artifice subtle and profound enough to depict the truth and reflect the sincerity of his feelings.