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The ''play of images'' determined by <math>\underline{f}</math> and <math>x,\!</math> more specifically, the play of the imagination <math>\underline{f} = (f_1, \ldots, f_k)</math> that has to do with the element <math>x \in X,</math> is the <math>k\!</math>-tuple <math>\underline{y} = (y_1, \ldots, y_k)</math> of values in <math>\underline\mathbb{B}</math> that satisfies the equations <math>y_j = f_j (x),\!</math> for <math>j = 1 ~\text{to}~ k.</math>
 
The ''play of images'' determined by <math>\underline{f}</math> and <math>x,\!</math> more specifically, the play of the imagination <math>\underline{f} = (f_1, \ldots, f_k)</math> that has to do with the element <math>x \in X,</math> is the <math>k\!</math>-tuple <math>\underline{y} = (y_1, \ldots, y_k)</math> of values in <math>\underline\mathbb{B}</math> that satisfies the equations <math>y_j = f_j (x),\!</math> for <math>j = 1 ~\text{to}~ k.</math>
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<pre>
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A ''projection'' of <math>\underline\mathbb{B}^k,</math> written <math>\pi_j\!</math> or <math>\operatorname{pr}_j,\!</math> is one of the maps <math>\pi_j : \underline\mathbb{B}^k \to \underline\mathbb{B},</math> for <math>j = 1 ~\text{to}~ k,</math> that is defined as follows:
A "projection" of Bk, typically denoted by "pj" or "prj", is one of the maps pj : Bk �> B, for = 1 to k, that is defined as follows:
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If v = <v1, ..., vk> C Bk,
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{| align="center" cellpadding="8" width="90%"
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|
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<math>\begin{array}{cccccc}
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\text{If} & \underline{y} & = & (y_1, \ldots, y_k) & \in & \underline\mathbb{B}^k, \\
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\\
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\text{then} & \pi_j (\underline{y}) & = & \pi_j (y_1, \ldots, y_k) & = & y_j. \\
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\end{array}</math>
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|}
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then pj(v) = pj(<v1, ..., vk>) = vj.
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The ''projective imagination'' of <math>\underline\mathbb{B}^k</math> is the imagination <math>(\pi_1, \ldots, \pi_k).</math>
 
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The "projective imagination" of Bk is the imagination <p1, ..., pk>.
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<pre>
 
A "sentence about things in the universe", for short, a "sentence", is a sign that denotes a proposition.  In other words, a sentence is any sign that denotes an indicator function, any sign whose object is a function of the form f : U �> B.
 
A "sentence about things in the universe", for short, a "sentence", is a sign that denotes a proposition.  In other words, a sentence is any sign that denotes an indicator function, any sign whose object is a function of the form f : U �> B.
  
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