In 1796 he published the first volume of his most successful work, A Philosophical and Practical Treatise on Horses and on the Moral Duties of Man towards the Brute Creation.

In his New Farmer's Calendar (1800) and The Modern Land Steward (1801) he advocated for killing food animals painlessly.

Lawrence was also quoted extensively in Henry Stephens Salt's 1894 Animals' Rights: Considered in Relation to Social Progress.

In his 1796 "Philosophical and Practical Treatise on Horses", Lawrence wrote of the rights of animals: They arise then, spontaneously, from the conscience, or sense of moral obligation in man, who is indispensably bound to bestow upon animals, in return for the benefit he derives from their services, "good and sufficient nourishment, comfortable shelter, and merciful treatment; to commit no wanton outrage upon their feelings, whilst alive, and to put them to the speediest and least painful death, when it shall be necessary to deprive them of life.

I therefore propose, that the Rights of Beasts be formally acknowledged by the state, and that a law be framed upon that principle, to guard and protect them from acts of flagrant and wanton cruelty, whether committed by their owners or others.