title: Material-UI v1: How to set one font size for all the components in material-ui v1?
body: <p>We are using 1.4.5 material-ui in our application. Now we are trying to set one font size for all of the components in our application. For example we want to set <code>fontSize: 14px,</code> for headers / buttons / paragraph /list... and so on. 
  Here is our sample theme configuration: </p>
  
  <pre><code>import { createMuiTheme } from '@material-ui/core/styles';
  import purple from '@material-ui/core/colors/purple';
  import green from '@material-ui/core/colors/green';
  
  const theme = createMuiTheme({
    typography: {
      fontSize: 14,
    },
    palette: {
      primary: purple,
      secondary: green,
    },
    status: {
      danger: 'orange',
    },
  });
  </code></pre>
  
  <p>If you notice we have tried to define the font size in a <code>typography</code> object but  with this configuration, material-ui computes a font size according to the formula given at <a href="https://material-ui.com/customization/themes/#typography-font-size" rel="noreferrer">this link.</a></p>
  
  <p>We are trying to achieve a 14px font-size application wide but we can not find an option to do this. One option can be a <code>pxToRem</code> function but I am not sure how should I overwrite that function and what should be my function?  The other option is to define styles in every component and I think that is a bit overkill since we should able to do it with theme object. 
  Please help me if you can think of a way to set the font size globally. 
  Your help will be greatly appreciated. </p>