There was an infamous remark made in 1609 by a savant named Theodore Baronius when , demonstrating the blind attachment to the ancient received wisdom of the Greek physician named Galen, he asserted he would find it preferable to err with Galen than to be right with any other man. This is drastic dedication, especially for a man of what passed for science; but it strikes a familiar chord, perhaps, because we can all recognize in ourselves the comfort taken from being in agreement with others. Especially an agreement of long historicity, attributed to ancient mastery, and widely held. Nothing more comfortable than a good solid set of stable beliefs supported by wide-spread agreement, whose origin seems to disappear in the mists of history, beyond all calling to account. It took over fifty years for Harvey’s insights to become generally accepted instead of Galen’s model of blood ebbing and flowing in tides, into which various humours were mixed by glands which caused personality traits.
Prior to Harvey’s surprising discoveries of the heart’s pump and the purpose of veins, arteries, and capillaries the notion of humours and tides of the blood was widely held as established knowledge. Generations agreed with their teachers, and the idea of actual inspection of facts was often considered heretical. Harvey’s remark on the rigidity of past thoughts sums up the risk he took in breaking with the Galenic model: “So much does custom, or teaching once accepted and fixed by deep roots, weigh with all ; and such is the influence of the venerable opinion of antiquity. However this may be, now that the die is cast, my hope lies in the candour of lovers of truth and of learned minds.”
Harvey’s trials eventually receded, but he was seriously nettled by the controversy which rose up in the face of his earnest scientific explanations; he referred to the tide of human opinion as “a faithless sea”. Be that as it may, what is of enduring interest from his tale is the power and mechanism of agreement. The power of agreement is such that entire currents of social belief can be swung, created, and evaporated by the wise use of it, by one who understands the ways of agreement-making and -breaking. In a sense, it is the woof on the loom of reality itself.
Consider some subject about which you have not made many agreements—say, car engines or electronics, or celestial navigation. The things of that field will be thin gruel, mentally, for you, compared to the clarity of reality obtained by someone who has agreed with the names and mechanisms and patterns which describe it. The parts of an oboe are a remote mystery to most people, who do not generally communicate much with oboes in their lives. To some people the parts of a car are a cloud of mysterious bits which comprise an attitude, such as “My car loves me!” They have ignored the agreements about these various parts and how they combine. They may substitute strange alternatives, such as having spirit guides find them parking places or God fixing the radiator. Someone else might have a detailed sense of the reality of camshafts, pistons, tappets and timing chains but know nothing about the chemistry of combustion which makes them move. These things comprise a set of agreements that they have not made.
The possibility needs to be considered that the reality of the universe itself hinges on the multiplex of agreements made about it.
Agreeing about something induces the ability to see it more clearly as agreed-on. This is why new spaces get brighter and more vivid as you explore them and start building up agreements about them. We make agreements about what is there, and take comfort in sharing the certainties of what we see. We also agree with our own created considerations, thus making them more solid and permanent.
To break a set of agreements upsets the reality of others who share it; this was Harvey’s transgression, and also Ignaz Semmelweiss’, when he insisted on hygiene procedures in maternity wards, and Henry Ford’s when he paid his labor force a dramtically high wage so they could buy his cars. In his book The Game of Life, Timothy Leary provided the following polemical definition of the Semmelweis reflex: "Mob behavior found among primates and larval hominids on undeveloped planets, in which a discovery of important scientific fact is punished".
Each of these cases demonstrated a dramatic improvement in the operating conditions and understanding at the time, but the people who made those bold steps had to pay the price of shaking up those whose agreements they were breaking. It is possible that with a better sense of public relations, the changes they sought could have been made less controversial; but genius and PR are usually distant cousins at best.
 William Harvey. 'Exercitationes Anatomicae.', Exercitatio I. cap. Viii, ed. 1660
 Carter, K. Codell; Carter, Barbara R. (February 1, 2005), Childbed fever. A scientific biography of Ignaz Semmelweis, Transaction Publishers, ISBN 978-1-4128-0467-7