This is Just to Say Analysis by William Carlos Williams

I have eaten
the plums

The speaker opens the poem with these lines (lines 1–2), in which they confess to an act of wrongdoing. As suggested by the plainspoken language, the speaker has nothing invested in trying to evade responsibility for their actions. Instead, they own up to the act in the clearest and most upfront way imaginable. Despite how casual and ordinary the opening lines are, a shrewd reader could interpret the speaker’s admission as an echo of the Catholic rite of confession. In Catholicism, believers periodically confess their sins to a representative of the Church, typically a priest. The opening of the confession is scripted in such a way that the sinner begins the rite by plainly stating that they have done wrong: “Bless me, Father, for I have sinned.” Although such a reading may seem forced given the lack of artifice in the speaker’s language, it’s worth noting that the opening lines anticipate a later line where the speaker explicitly begs pardon: “Forgive me” (line 9). The language of forgiveness is pertinent here, especially considering that Catholics perform the rite of confession to ask for God’s forgiveness and thereby cleanse themselves of sin.

you were probably
saving
for breakfast

These lines (lines 6–8) appear in the second stanza, where the speaker acknowledges how their actions may have affected the person they are addressing. Specifically, the speaker reflects that the addressee may have put the plums in the icebox to save them for later use. By taking and eating the last of the plums, the speaker has likely inconvenienced this other person. In saying these words, the speaker clearly shows that they’ve reflected on the harm their actions of caused. If we accept the reading suggested above regarding the poem’s evocation of the Catholic confession rite, then we can interpret the speaker’s reflection as a key component of their request for forgiveness. In Catholicism, a sinner can only be forgiven if they are honestly penitent. One way to demonstrate penitence is to verbally articulate an understanding of how one’s actions have caused harm, either to others or to God. According to a symbolic reading like this, the speaker’s words here prepare the addressee to receive a request for forgiveness.

they were delicious
so sweet
and so cold

The speaker closes the poem with these lines (lines 10–12). Whereas the first two-thirds of the poem may be read as an ordinary version of the Catholic rite of confession, these lines make a decisive break away from the Catholic notions of sin and penitence. Indeed, these lines shift the focus from negative implications of taking the plums to the sheer pleasure the speaker experienced in eating them. In one way, we could read these lines as an excuse. That is, the speaker couldn’t help themself, since the plums were too delicious to resist. In other way, though, we could read the poem’s closing lines as a quiet celebration of one of life’s simple pleasures. Read in this way, the closing lines may in fact subtly undermine the speaker’s plea for forgiveness and gently chide the addressee instead. Whereas the addressee wanted to keep the plums locked away in the icebox for later, the speaker emphasizes the value of enjoying them now. To return to the religious symbolism suggested in the rest of the poem, this ending suggests the importance of living for the present moment rather than preserving oneself for rewards in the afterlife.