{
  "aliases": [
    "quantifier-order"
  ],
  "backlinks": null,
  "body": "\n## Summary\n\nIn a statement with several quantifiers, the order of different quantifiers changes the meaning.\nFor a [[predicate|0T3DPBG981]] $P(x, y)$, the statement $\\exists y \\, \\forall x \\, P(x, y)$ implies $\\forall x \\, \\exists y \\, P(x, y)$, but the converse is false in general.\nTwo quantifiers of the same type commute: $\\forall x \\, \\forall y \\, P(x, y)$ is equivalent to $\\forall y \\, \\forall x \\, P(x, y)$, and the same holds for $\\exists$.\n\n## Remarks\n\nOn the integers, $\\forall x \\, \\exists y \\, (y \u003e x)$ is true, but $\\exists y \\, \\forall x \\, (y \u003e x)$ is false.\nIn $\\forall x \\, \\exists y$, the choice of $y$ can depend on $x$.\nThe definitions of continuity and of uniform continuity differ only in the order of quantifiers.\n\n## Explanations\n\n### L1 human\n\n\"Every person has a mother\" is $\\forall x \\, \\exists y$: each person has their own mother.\n\"Some person is the mother of every person\" is $\\exists y \\, \\forall x$: one mother for all.\nThe first sentence is true, and the second is false.\n",
  "commit": "6ac761d40018146541484a9e8b9eafd6ecc303dc",
  "front": {
    "aliases": [
      "quantifier-order"
    ],
    "kind": "concept",
    "msc": [
      "03B10"
    ],
    "name": "Order of quantifiers",
    "same_as": {
      "wikidata": "Q592911",
      "wikipedia": "Quantifier (logic)"
    },
    "sources": [
      {
        "locator": "lead section",
        "url": "https://en.wikipedia.org/wiki/Quantifier_(logic)"
      }
    ],
    "tag": "0FYQMKFE77",
    "uses": [
      "0B88PQTJ66",
      "0JW2FHW7G3"
    ]
  },
  "kind": "concept",
  "link": "https://math2.tamnd.com/node/0FYQMKFE77/",
  "links": [
    {
      "field": "uses",
      "target": "0B88PQTJ66"
    },
    {
      "field": "uses",
      "target": "0JW2FHW7G3"
    }
  ],
  "markdown": "https://math2.tamnd.com/node/0FYQMKFE77.md",
  "msc": [
    "03B10"
  ],
  "name": "Order of quantifiers",
  "prov": null,
  "role": "",
  "source": "https://github.com/tamnd/math2/blob/main/nodes/0FY/0FYQMKFE77.md",
  "status": null,
  "tag": "0FYQMKFE77",
  "uri": "m2://0FYQMKFE77",
  "url": "https://math2.tamnd.com/wiki/order-of-quantifiers/",
  "writing": {
    "tag": "0FYQMKFE77",
    "kind": "concept",
    "level": "W1",
    "next": [
      {
        "what": "edge defines in",
        "note": "at least one definition",
        "have": 0,
        "want": 1
      },
      {
        "what": "edge instance_of in",
        "note": "at least two examples",
        "have": 0,
        "want": 2
      },
      {
        "what": "edge not_instance_of in",
        "note": "at least one non-example",
        "have": 0,
        "want": 1
      },
      {
        "what": "edge specializes both",
        "note": "the more general notions and the special cases",
        "have": 0,
        "want": 1
      }
    ]
  }
}
