Definition of "notion"

What hath been generally agreed on, I content myself to assume under the notion of principles.

1704, I[saac] N[ewton], “(please specify |book=1 to 3)”, in Opticks: Or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light. […], London: […] Sam[uel] Smith, and Benj[amin] Walford, printers to the Royal Society, […]

there are few that agree in their Notions about them:.

1705-1715', George Cheyne, The Philosophical Principles of Religion Natural and Revealed

That notion of hunger, cold, sound, color, thought, wish, or fear which is in the mind, is called the "idea" of hunger, cold, etc.

1725, Isaac Watts, Logick: Or, The Right Use of Reason in the Enquiry after Truth, […], 2nd edition, London: […] John Clark and Richard Hett, […], Emanuel Matthews, […], and Richard Ford, […], published 1726

Notion, again, signifies either the act of apprehending, signalizing, that is, the remarking or taking note of, the various notes, marks, or characters of an object which its qualities afford, or the result of that act.

1859–1860, William Hamilton, edited by H[enry] L[ongueville] Mansel and John Veitch, Lectures on Metaphysics and Logic […], volumes (please specify |volume=I to IV), Edinburgh, London: William Blackwood and Sons

The extravagant notion they entertain of themselves.

1715 April 13 (Gregorian calendar), Joseph Addison, “The Free-holder: No. 30. Saturday, April 2. ”, in The Works of the Right Honourable Joseph Addison, Esq; […], volume IV, London: […] Jacob Tonson, […], published 1721

A perverse will easily collects together a system of notions to justify itself in its obliquity.

December 2, 1832, John Henry Newman, Wilfulness, the Sin of Saul

“Anthea hasn't a notion in her head but to vamp a lot of silly mugwumps. She's set her heart on that tennis bloke […] whom the papers are making such a fuss about.”

1935, George Goodchild, chapter 1, in Death on the Centre Court

Who wrought with them, and all things else that might / To half a soul and to a notion crazed / Say, 'Thus did Banquo.'

c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act III, scene i], page 140