Trinity and Socinianism
The Trinity does not have the status of an optional extra in his theology, but represents the necessary ontological framework of his entire soteriology. This is why he regards Socinianism, with its basic denial of orthodox trinitarianism, as such a pernicious heresy: to reject the Trinity involves the wholesale rejection of Christian theology.
Carl Trueman, Claims of Truth: John Owen's Trinitarian Theology (Grand Rapids, MI: Reformation Heritage Books, 2021), 28