{"id":40434,"date":"2017-10-20T15:32:11","date_gmt":"2017-10-20T14:32:11","guid":{"rendered":"https:\/\/blogs.bmj.com\/bmj\/?p=40434"},"modified":"2017-10-27T16:17:23","modified_gmt":"2017-10-27T15:17:23","slug":"jeffrey-aronson-when-i-use-a-word-modes-of-speech-can-and-may-must-and-should","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/bmj\/2017\/10\/20\/jeffrey-aronson-when-i-use-a-word-modes-of-speech-can-and-may-must-and-should\/","title":{"rendered":"Jeffrey Aronson: When I use a word . . . Modes of speech: can and may, must and should"},"content":{"rendered":"<p><a href=\"https:\/\/blogs.bmj.com\/bmj\/files\/2014\/12\/jeffrey_aronson.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft wp-image-32935\" src=\"https:\/\/blogs.bmj.com\/bmj\/files\/2014\/12\/jeffrey_aronson-223x300.jpg\" alt=\"jeffrey_aronson\" width=\"112\" height=\"151\" srcset=\"https:\/\/blogs.bmj.com\/bmj\/files\/2014\/12\/jeffrey_aronson-223x300.jpg 223w, https:\/\/blogs.bmj.com\/bmj\/files\/2014\/12\/jeffrey_aronson.jpg 446w\" sizes=\"auto, (max-width: 112px) 100vw, 112px\" \/><\/a><span style=\"font-weight: 400\">Which is better: \u201cAspirin can cause Reye\u2019s syndrome\u201d or \u201cAspirin may cause Reye\u2019s syndrome\u201d? The answer lies in a consideration of modal verbs, also called modal auxiliaries.<\/span><\/p>\n<p><span style=\"font-weight: 400\">Modal verbs are used to express modality, in other words, they modify the meaning of a verb, indicating how to interpret it. The main (or central) modal verbs are \u201ccan\u201d, \u201ccould\u201d, \u201cshall\u201d, \u201cshould\u201d, \u201cwill\u201d, \u201cwould\u201d, \u201cmay\u201d, \u201cmight\u201d, and \u201cmust\u201d; the semi-modal (or marginal modal) verbs are \u201cought to\u201d, \u201cused to\u201d, \u201cdare [to]\u201d, and \u201cneed [to]\u201d. They have three uses.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400\"><i><span style=\"font-weight: 400\">Epistemic<\/span><\/i><span style=\"font-weight: 400\"> modal verbs (Greek \u1f10\u03c0\u03b9\u03c3\u03c4\u03ae\u03bc\u03b7, knowledge) express the truth or likelihood of a proposition, i.e. whether it is possible, probable, or necessarily true. For example: \u201cAspirin may cause Reye\u2019s syndrome\u201d [in general, with a particular probability]; \u201cAspirin might cause Reye\u2019s syndrome\u201d [in this case, with a particular probability]; \u201cThe aspirin must have caused Reye\u2019s syndrome\u201d [for certain, in this case].<\/span><\/li>\n<li style=\"font-weight: 400\"><i><span style=\"font-weight: 400\">Deontic<\/span><\/i><span style=\"font-weight: 400\"> modal verbs (Greek<\/span> <span style=\"font-weight: 400\">\u03b4\u03ad\u03bf\u03bd, binding) express directives or permission. For example: \u201cYou must prescribe aspirin\u201d [an imperative]; \u201cYou should or ought to prescribe aspirin\u201d [preferably, unless something dictates otherwise]; \u201cYou may prescribe aspirin\u201d [in this case, if it seems appropriate]; \u201cYou might prescribe aspirin\u201d [in general, if it were indicated]; \u201cI don\u2019t dare prescribe aspirin for this child\u201d; \u201cYou need not prescribe aspirin in this case\u201d.<\/span><\/li>\n<li style=\"font-weight: 400\"><i><span style=\"font-weight: 400\">Dynamic<\/span><\/i><span style=\"font-weight: 400\"> modal verbs (Greek<\/span> <span style=\"font-weight: 400\">\u03b4\u03cd\u03bd\u03b1\u03bc\u03b9\u03c2 power or strength) ascribe ability or volition. For example: \u201cAspirin can cause Reye\u2019s syndrome\u201d.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400\">There is much ambiguity in these words. For example, although \u201ccan\u201d strictly speaking denotes ability, knowing how to or being able to, it is also used to denote possibility (\u201cYes we can\u201d, which implies both ability and possibility) or permission (\u201cYes, you can\u201d).<\/span><\/p>\n<p><span style=\"font-weight: 400\">If you say \u201cAspirin <\/span><i><span style=\"font-weight: 400\">can<\/span><\/i><span style=\"font-weight: 400\"> cause Reye\u2019s syndrome\u201d, you are implying that there is a known cause and effect association between the drug and the event, in other words that aspirin is capable of causing the syndrome, as is <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/17147458\"><span style=\"font-weight: 400\">generally accepted<\/span><\/a><span style=\"font-weight: 400\">.<\/span><\/p>\n<p><span style=\"font-weight: 400\">On the other hand, if you say \u201cAspirin <\/span><i><span style=\"font-weight: 400\">may<\/span><\/i><span style=\"font-weight: 400\"> cause Reye\u2019s syndrome\u201d in a general sort of way, you are implying that the association is suspected but not proven. If you say it in relation to an individual, you are implying that the use of aspirin in this case is a hazard, with a chance of harm. In both cases you will have some sort of probability in mind.<\/span><\/p>\n<p><span style=\"font-weight: 400\">There is little doubt about all this in the case of aspirin, but if you were to say that a new medication \u201ccan\u201d cause some adverse reaction, you might be accused of falsely implicating the medicine as a general cause of the reaction, if the evidence was not satisfactory or contended. It would generally be better in that case to say \u201cmay\u201d or \u201cmight\u201d.<\/span><\/p>\n<p><span style=\"font-weight: 400\">As <a href=\"https:\/\/blogs.bmj.com\/bmj\/2017\/09\/22\/jeffrey-aronson-when-i-use-a-word-competence\/\">I have previously pointed out<\/a>, the UK\u2019s General Medical Council defines the words \u201cmust\u201d and \u201cshould\u201d in relation to its various pieces of guidance for doctors, as follows:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">\u201c\u2018You must\u2019 is used for an overriding duty or principle.\u201d<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">\u201c\u2018You should\u2019 [prefaces] an explanation of how you will meet the overriding duty.\u201d<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">\u201c\u2018You should\u2019 is also used where the duty or principle will not [always] apply, or where . . . factors outside your control . . . affect whether or how you can follow the guidance.\u201d<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400\">Now, in its <\/span><a href=\"http:\/\/www.gmc-uk.org\/guidance\/ethical_guidance\/14323.asp\"><span style=\"font-weight: 400\">Prescribing guidance: Reporting adverse drug\/device and other patient safety incidents<\/span><\/a><span style=\"font-weight: 400\">, the GMC writes \u201cYou must inform the MHRA [the medicines regulatory agency in the UK] about . . . serious suspected adverse reactions to all medicines and all [sc. suspected] reactions to products marked with a Black Triangle in the BNF and elsewhere using the Yellow Card Scheme.\u201d However, reporting in this way is not mandatory in the UK. It is mandatory in some countries, such as <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/21050790\"><span style=\"font-weight: 400\">France<\/span><\/a><span style=\"font-weight: 400\">, <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/21985831\"><span style=\"font-weight: 400\">Denmark<\/span><\/a><span style=\"font-weight: 400\">, and <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/18470952\"><span style=\"font-weight: 400\">Korea<\/span><\/a><span style=\"font-weight: 400\">, but in <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pubmed\/19390246\"><span style=\"font-weight: 400\">Japan<\/span><\/a><span style=\"font-weight: 400\"> the proposed introduction of a mandatory system for reporting fatal adverse events led to widespread fear of prosecution and defensive medicine; physicians started to refuse to see high risk patients and referrals to other hospitals became widespread; medical school graduates began to avoid specialties that were perceived as being legally particularly vulnerable, and various hospitals and clinics had to close.<\/span><\/p>\n<p><span style=\"font-weight: 400\">It\u2019s not that UK doctors must not report suspected adverse reactions, but not that they must.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft wp-image-40441\" src=\"https:\/\/blogs.bmj.com\/bmj\/files\/2017\/10\/aronson_modeofspeech_reye.jpg\" alt=\"\" width=\"233\" height=\"233\" \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-40440\" src=\"https:\/\/blogs.bmj.com\/bmj\/files\/2017\/10\/aronson_modeofspeech.png\" alt=\"\" width=\"442\" height=\"243\" srcset=\"https:\/\/blogs.bmj.com\/bmj\/files\/2017\/10\/aronson_modeofspeech.png 460w, https:\/\/blogs.bmj.com\/bmj\/files\/2017\/10\/aronson_modeofspeech-300x165.png 300w\" sizes=\"auto, (max-width: 442px) 100vw, 442px\" \/><\/p>\n<p><span style=\"font-weight: 400\">Ralph Douglas Kenneth <\/span><a href=\"http:\/\/adb.anu.edu.au\/biography\/reye-ralph-douglas-kenneth-11511\"><span style=\"font-weight: 400\">Reye<\/span><\/a><span style=\"font-weight: 400\"> (1912\u201377), who, with Graeme Morgan and Jim Baral, described what we now call Reye\u2019s syndrome in 1963 (Reye RD, Morgan G, Baral J. Encephalopathy and fatty degeneration of the viscera. a disease entity in childhood. <em>Lancet<\/em> 1963; 2(7311): 749-52); I guess that the surname Reye (pronounced rye) is a variant of the Spanish word for a king, rey.<\/span><\/p>\n<p><em><strong>Jeffrey Aronson<\/strong>\u00a0is a clinical pharmacologist, working in the Centre for Evidence Based Medicine in Oxford&#8217;s Nuffield Department of Primary Care Health Sciences. He is also president emeritus of the British Pharmacological Society.<\/em><\/p>\n<p><strong>Competing interests:<\/strong>\u00a0None declared.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Which is better: \u201cAspirin can cause Reye\u2019s syndrome\u201d or \u201cAspirin may cause Reye\u2019s syndrome\u201d? The answer lies in a consideration of modal verbs, also called modal auxiliaries. Modal verbs are [&#8230;]<\/p>\n<p><a class=\"btn btn-secondary understrap-read-more-link\" href=\"https:\/\/blogs.bmj.com\/bmj\/2017\/10\/20\/jeffrey-aronson-when-i-use-a-word-modes-of-speech-can-and-may-must-and-should\/\">More&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":38359,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5762],"tags":[],"class_list":["post-40434","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-jeff-aronsons-words"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Jeffrey Aronson: When I use a word . . . Modes of speech: can and may, must and should - The BMJ<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.bmj.com\/bmj\/2017\/10\/20\/jeffrey-aronson-when-i-use-a-word-modes-of-speech-can-and-may-must-and-should\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Jeffrey Aronson: When I use a word . . . Modes of speech: can and may, must and should - The BMJ\" \/>\n<meta property=\"og:description\" content=\"Which is better: \u201cAspirin can cause Reye\u2019s syndrome\u201d or \u201cAspirin may cause Reye\u2019s syndrome\u201d? The answer lies in a consideration of modal verbs, also called modal auxiliaries. 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