Writing\Proposition

A statement intended to convey information that something is true; composed of declarative sentences.

A declarative sentence is defined [Hodges 1977, p. 19] as a grammatical sentence that can be substituted for ‘x’ in the question:

Is it true that x?

A proposition may consist of a single declarative sentence (an atomic proposition) or one or more declarative sentences joined by logical operators (a compound proposition).

A single declarative sentence may be modified by:

• logical negation; the ‘not‘ operator

or connected with other declarative sentences by:

• logical conjunction; the ‘and‘ operator
• logical disjunction; the ‘or‘ operator
• exclusive disjunction; the ‘either_or‘ operator

The precedence or binding of operators can be confirmed or modified by the use of parentheses.  For further details of the logical operators, select from the ‘Writing\Proposition’ menu above.

Interface Detail

To enter a declarative sentence click on the text-box highlighted in dark yellow.  It changes to bright yellow to indicate that it has been selected and a declarative sentence may be typed in.

As each declarative sentence is entered, Pacisco searches to see if a similar claim has already been asserted.  Potential matches are listed below the text box.  If an appropriate match is found it should be selected by clicking on it and it will replace the typed text.

To input logical operators, ensure that the declarative sentence to which you wish to apply the operator has been selected (highlighted in bright yellow) and then click on the appropriate button.  The operator will be inserted into the proposition and, if appropriate, a selected text-box in which to enter another declarative sentence will have opened.

Declarative sentences or operators entered in error can be removed by clicking on the item to select it and then clicking the ‘Erase’ button.  When an operator is selected its operands  are also highlighted.  Clicking the erase button will remove the operator and the right most operand, leaving the leftmost operand untouched.