The soul controls "the state, the splendour and the throne, / An intellectual kingdom, all her own" 
Tirocinium: or, A Review of Schools.
At least 6 entries in the ESTC (1786, 1787, 1788, 1790, 1791, 1792, 1793, 1794, 1795, 1798, 1799, 1800).<br>
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See <u>Poems, by William Cowper, of the Inner Temple, Esq. Volume the Second. Containing the Task. An Epistle to Joseph Hill, Esq. Tirocinium, or a Review of Schools. And the History of John Gilpin.</u> 2nd ed. (London: Printed for J. Johnson, No. 72, St. Paul’s Church-Yard, 1786). &lt;<a href="http://estc.bl.uk/T14892">Link to ESTC</a>&gt;<br>
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Reading <u>The Poems of William Cowper</u>, eds. John D. Baird and Charles Ryskamp (Oxford: Oxford UP: 1980), vol. 2 of 3.